Emotiva XPA5 Gen 1

Emotiva amps are very good for the money, but there are definitely better amps. If you really need a 5 channel amp with that much power, it’s hard to beat Emotiva. However, stock Emotiva is quit bright. I have found you can tame an Emotiva pretty okay by switching out the fuses to Isoclean (adds warmth and takes the edge off the brightness).

If you are only doing 2-channel music, it’s better to put that money towards a better amp. Class D is a good technology that is efficient and provides a lot of power for the size. However, compromises are made in the circuit architecture which essentially translates to inability in the higher frequencies. These can be presented as a flatter more sterile sound. It depends on your listening.  I have found Class D to lack air, life and excitement.

I would probably look towards something like a Parasound A23 and upgrade the fuse to silver Hi Fi Tuning Supreme. Parasound 2125 is another good one for less money. Odyssey Audio Khartago is an excellent option. These are all in the "under $600" range.

Both of these amps are very old.  I used to own Adcom amp (GFA545) and it was great for a first amp in my journey.  However, I found it was very dirty sounding and low resolution.  Both of these amps (Adcom/Acurus) are very warm and laid back sounding.  If you want that kind of sound, then I would probably recommend Acurus as the better quality component.

Sounds like you are looking for local ads only?  Do you have a dislike for internet sales? 

Parasound 2125 from TMR Audio ($400):

http://tmraudio.com/components/power-amplifiers/parasound-model-2125-stereo-power-amplifier/

Parasound 275 V2 (newer model) from TMR Audio ($379)

http://tmraudio.com/components/power-amplifiers/parasound-model-newclassic-275-v-2-stereo-power-amplifier/

Odyssey Khartago ($525):

https://www.audiogon.com/listings/lis90340-odyssey-audio-khartago-tube

All of these are from reputable sellers (TMR is a retailer that has excellent customer service).  Any of these will be better than Adcom/Acurus.  They will have more resolution and attack  (more detail in the music).

My same comments on Emotiva XPA-5 also apply to A-300.  If you really want a brand new amp with that much power, Emotiva is hard to beat.  But you can easily get a used amp that is significantly better!

Emotiva Preamp - same thing.  They are rather lackluster in the midst of other preamps, but if you really want a NEW product, it's hard to beat. 

Preamps are actually a lot harder to buy cheaply than amps.  You have to spend a good amount of money before you are able to get something decent.  If you are looking for sound quality, this Vincent is probably the minimum I would recommend (it's all manual source selection and volume - no remote):

http://tmraudio.com/components/preamplifiers/vincent-sa-31-stereo-line-preamplfier-sa31/

The Vincent is actually a quite excellent performer.  It get's hard to find a good preamp without spending $600-700 or more.  If you want bargain basement, look at Schiit Saga. You can then upgrade the tube to something like Electro-Harmonix 6SN7 to get better resolution.

http://www.schiit.com/products/saga

If you're willing to spend more, Schiit Freya for $699 is outstanding.

If you want to stay on the solid-state side, Parasound P5:

https://www.usaudiomart.com/details/649439594-selling-parasound-p5/

Hope this helps.

For your subwoofer, you will most likely have to get a couple RCA splitter cables like the following:

https://www.amazon.com/AudioQuest-splitter-female-15-24cm-cable/dp/B000GUSQJG/ref=sr_1_2?ie=UTF8&qid=1528944801&sr=8-2&keywords=audioquest+splitter

You would connect the splitter cables to the right/left RCA outputs on your preamp.  The splitters allow you to further connect separate left/right RCA cables to the amp (for main speakers) and to the subwoofer inputs.

Sometimes you can get an amp that has 2 sets of RCA outputs.  The Vincent has two sets.   On your Onkyo preamp, you can use the single RCA subwoofer output on the back/top for the Klipsch subwoofer.  Just connect it to either the left or right input on the sub.

NOTE: Even though the Schiit preamps have 2 sets of outputs, you can only use one at a time.

The Parasound P5 actually has an analog crossover built in so that you can split the frequencies between MAIN RCA outputs as separate SUB RCA outputs.