What can I do to improve my 2nd system?

For the speakers, power amp and CD/SACD player, I have attached semisphere rubber isolators (made by 3M) underneath. Would that suffice? But the audio graded stand is definitely good idea.

I had a old sub by Audio Research (AR SW30) and I hooked both of them in stereo mode using the RCA splitter out of DAC. To integrate them together, I experimented several location and found placing both of them inside the L/R speakers is the best location. And I also need to set the phase on the 2nd sub. to "90 degree" to get them better paired together. However, for some reason, the AR sub seems to have hard time to keep up with SVS pacewise. I may need to purchase the same sub. if going for dual.

Here is my curiosity. I understand the 2nd sub is mainly used to mitigate the hump/null and obtain more even low end frequency distribution in the room. Also, having two subs helps headroom for each of them to play more effortlessly. If my seating position is always at the same spot and I was alone listener 99% of time, given the size of my room do I really need a 2nd sub? I was told by SVS tech a single sub. is sufficient given the size of my room. What are "other" advantages having the 2nd sub?

For room treatment, I was thinking placing the bass traps on L/R corners and the sound absorption panels on the 1st reflection points left and right. On the front wall (behind the main speakers), I have difficult time to do sound diffusion because of the windows but, question, may the blinds work as the diffusers (sort of) to my favor? If not, how about thick lining curtain?  What are the right way to treat that?  

@russ69 That was a very good idea. I was thinking about the heavy/thick drapes behind the speakers but what is "open" drapes?  And what is the purpose of the openess?  Let the sound wave pass through the drapes and be traped between the drapes and window?

@russ69 Thank you for the clarification

@erik_squires I was thinking about "upgrading" to the SVS SB 1000 "Pro" version that has the 3-band EQ feature at a trade-off of losing HPF capability.  Later I learned I could add an in-line HPF on the loop back to power amp but had a worry on the quality of in-line filter.  It is a trade-off.  The other option will be the miniDSP that you have alluded before on the other tread.  I need to give it a bit more thought.

Here comes with an interesting suggestion you have "crossing the speakers in front of you..."  To be frank, I have never thought about that.  The most toe-in I have attempted or suggested from other sources is pointing to the listener's position.  The laterally reflected indirect sound is reduced but the speakers become too bright on my face from these Elac bookshelf.  So I gradually reset it back and finally dialed in this slight toe-in angle.  Without the absorption treatment, I actually experienced a bit more spacious sound stage (believe or not).  I read about the "Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms" book by Floyd Toole.  He actually pointed out that some people actually like stronger lateral reflection because of the augmented sound stage and I think that might be the effect I was experiencing with.

Nevertheless, "crossing in front of the listener" is definitely something new and I will try that...

Hi, Erik, I will try those excellent suggestions after I get home and embark on the miniDSP journey including room measurements.  I like out-of-the-box thinking and approach doing things.  Also thank you all gentlemen for the advises. 

@lewm You intrigue me to dig into the decoupler/isolator subject. Here are articles, some support it and some don't. Please take it with a grain of salt. I went through several bookshelfs, starting from my 1st (NHT SuperOne 2.1) 25 years ago, Tannoy Mercury F1, Sony SSCS 5 and currently this Elac. I placed the IsoNode isolator underneath without a second thought back then because, just like many others, I heard noticeable difference in bass, tighter and cleaner. The effect on the subwoofer is even more pronounced. I think very few audiophiles will debate the benefit of using damping isolators under the subwoofer. I compared the $50 SVS Soundpath isolators with $3.5 a set of four damping isolators you could get from Walmart.  Very subtle different.  As a band bass player a band in college, I could testify that is not a placebo effect.  

I place the similar IsoNode isolators under the gears including CD/SACD player to reduce the vibration.  With that, the gap under the player has increased to 1+ inch to help dissicipate the heat from Parasound to answer @slaw, although I do agree a audio grade rack placing them individually will be more ideal.  BTW, the heat from Parasound PA is much less than the Cambridge IA I had for being a similar class A/B design.

https://www.pro-tools-expert.com/production-expert-1/2019/5/23/speaker-isolation-fact-or-bullshit-we-have-the-results-from-the-poll?mc_cid=2a1503e520&mc_eid=f10a2ce15b

http://ethanwiner.com/speaker_isolation.htm

@erik_squires Finally got home after a long drive.  Play "The Wild Heart of the Earth" by Cécile Verny Quartet from Fear and Faith (album) to test out the "crossing in front of the listener" idea.  Immediately the first impression is the shrinkage of the sound stage.  Switching back to slight toe-in position and everything gets back to normal.  Sorry, Erik, as much as I appreciate the thought, I am not sold on this thinking outside the box idea.  However, with the height of the stands, I was actually listening below the vertical axis of tweeter all the time when I lean back on the recliner.

@stringreen I do not disagree the magic power of a good paring of headset and dedicated amp.  However, I could not endure wearing headset or In-ear even for half hour.  The discomfort from even a high-end headphone just sets off my enjoyment of music listening.   

Any suggestion that can work well with Parasound?

@russ69 Maybe you did not see my response to Erik. Crossing in front of the listener shrinks the soundstange, at least in my room.