Best €2500 sub purely for music?


I recently was lucky enough to try a demo between a two rel 9tx and one s510, and I though the s510 was vastly superior. My only hesitation for being one was that the EU pricing of rels are kinda steep, and maybe im not someone best suited to use them? To explain, I use a minidsp shd preamp to control my entire system. With that I always use a high-pass filter with a extremely sharp roll off of -48db. Anything above 60hz is given to the speakers. I found this to sound night and day better than trying to cross any speaker with their natural cutoff. This is antithetical to how rel designs their subs. Lastly, it only has phase adjustments of 0 and 180. Its for these reasons why im asking you if there are any alternatives to the s510 you recommend between €2k and €3k IN EUROPE (so no svs or rhythmic or any other US brand of any sort) that might be more appropriate for a purely hifi application?

My speakers are German physiks hrs-130's. They're omnidirectional, but what is important here is they a sealed design that is extremely precise and fast, but its not enough SPL for synthetic music. The lesser rel's arnt as fast as it, so I ask for something equivalent to the s series. I only want one, and my room is 30m^2. I will be using the full Dirac calibration of the shd to integrate it, so subs with on-board dsp is completely irrelevant, and I'd rather not spend on a feature that's useless to me. What other options are available here? 

endymion_joshi-godrez

I dont think many of you have heard a sub like a s510. We are talking about a subwoofer that retails for $2700 in the US, yet has less bass extention than a svs sb2000. There is a very good reason why it cost over 4 times more, which is why I was asking from people that do not use subwoofera for HT. A HT sub is simply not what I want, both because SPL was never an issue from the smaller rels I had, and the HT subs like the XTZ recommended to me have a bass presentation I dont like. They exaggerate bass, the mass majority of sub makers including kef, svs, JL and so on do that. I don’t want a sub like that. Rels dont, and apparently neither do rythmiks sealed subs. I want alternatives like that in the plus €2000 range. 

@endymion_joshi-godrez 

I have to disagree that no tower speakers can do bass well under 60 hz. My Rockport Avior ii speakers give me all the bass I need in my room. No subs. Also just pull the trigger on the S510s. We have 4 in our HT set up and they work great for 2 channel music too. The enjoyment will out way the price 

The rockports are WAY bigger and more expensive than my speakers, they need something like a no.25 or 32, and you will hear a noticeable improvement than without even a single. I think you're right, one thing abouts rels they seemly never break. There are still ebay auctions of rel stadium in working condition, thats around 30 years of use. I’ve yet to see anyone show me that they block one, while velodyne, JL, and B&W subs seem to have a tone of issues in the long term.

even monitors can do well under 60Hz, otherwise I wouldn't have a crossover mess with my sub.

@ronboco 

My Rockport Avior ii speakers give me all the bass I need in my room. No subs.

Counter-argument -- https://youtu.be/tGeNwgT18bA?t=39

You can reply, "I have a specially designed room."

That may defeat Paul's point -- for your room.

But, most people don't have a specially designed room.

Therefore, they might need subs even if they have full range speakers.