That being said a pair of SR71's are on my list to do this summer. Just got finished moving and need to get my woodworking shop back up and some honey-do's complete before I can play again. If you have the woodworking skillz and the time have you some fun and build any Zaph design or call Madisound and get some recommendations. I heave heard a lot of the SEAS speakers and they are sweet sounding, but hard to go wrong when they were driven by amps costing twice as much. if you are looking for clean low end, you would have to start with SR71's as the tuning cut off on the 5.X are set high as he designed them to be used with a powered sub.
Just my humble opinion, but given your power and budget I would start with a real nice sub design. I suspect you can do that for $300-400. if its output is adequate almost any good 2-way on Madisound's site can drive loud listening requirements when crossed over.
I would ask yourself this before you get too carried away on volume:
1. Do you have hearing damage that makes you listen loud? What frequency is the lossat ?
2. Have you had to get loud in the past to hear detail, you otherwise did not hear? (wrong speaker and/or amp combo)
3. Are you at a volume to overcome room noise floor....Do you need a bit of sound treatment?
Long term you want to enjoy what you have....
I find that the 5.3's I have more power than I could ever use with 16 watts.... so not really breaking 1 watt normally, so roughly 90db, at 1meter, and I am 2meters away....so 87db
The B&W's on the other hand, and room is 4x the volume of space.....my listening volume may be 95 decibels....100-105 of peaks in action movies.
Once I fix a rooms acoustics, amazing how the volume goes down. Even the 5.3's I feel a good thump with no sub at moderate volumes. Think of everything as a system, and make tweaks and you can easily get that budget.
Enjoy, and have fun with cabinets. If you are a woodworker you find that a sheet of $25 MDF goes a long way and you can build rough cabinets to get the feel for sound and aesthetics, then you build a set of cabinets you plan on keeping. Nothing quite works out design kinks like a full size test build.