Lots of detail, great imaging, not much bass?

Now that you've upped your budget I think a used pair of Joseph Audio RM7XLs would be very worth consideration given what you're looking for.

Also, I don't think tripling the wall thickness will do much for your bass problem although it may help a bit with the mids and highs (especially if you use something like green glue between the layers). The walls will still be attached to the studs, which will still vibrate with the bass and transmit to the wall on the other side. Plus, depending on construction the beams in the floors and ceilings will also continue to transmit bass to the other room. Unless you're willing/able to install something like resilient channels in your walls and, significantly more difficult, also isolate the floor and ceiling I don't think you'll be able to attenuate the bass transmission enough to allow you to crank the music very loud if it contains significant bass. Sorry to be a bummer but that's my understanding of it and don't want to see you waste $$$ on something that won't work, but maybe others have suggestions.

B-limo,
Just wondering, why not simplify system since moving into smaller quarter?

Get an excellent quality integrated amp with tone controls ~ (adjust bass as you wish) +
loudness boost (for late night/low level listening) + built-in headphone amp (ready when
adding one). This, I believe will suit your purpose better, whilst giving more flexibility and
less clutter too (happy fiancé). Only then on to speakers later ~ when/if still needed.

Something like a Luxman / Accuphase / Mc Intosh unit would be nice. Just saying..

*Btw. House music with little bass is like living with no soul. So you still do need that bass
reserves for when no one's looking! ;)

Soix, thanks for the input regarding bass transmission, as I was thinking that the triple layer, green glue would help with bass. I think really what I need to do is just wait until I move in and then do some sound tests with my music playing and then go down in there bedroom to see how bad the situation is going to be.

I really don't get why home builders (especially custom home builders at the price point that this home is; $800-$1m?) don't spray insulation in the floor joists in an attempt to help withnoise transmission through walls, floors and ceilings. It sure would help homeowners enjoy thier homes more if thier teenagers pounding techno music (or in this case, my pounding techno music) throughout the whole house. I love techno / house music but I can totally understand how utterly annoying it is when all you can hear is "boom boom boom boom boom".

B_limo, knowing all the facts now I think most important is having enough gain from your system and damping the room as you have wisely decided.
I've lived in apartments (new construction) where neighbors complained about my TV thru their walls.

So what you're telling me is that if I had more gain I'd get more detail, better imaging and less bass? Because that's what I'm after. And do you know how much gain I have in my system? Should I just replace my lightspeed attenuator, one of my favorite pieces? Ummm, okay...