Bookshelf/subwoofer combo

@OP In  room that size, you should consider a good pair of floorstanders. Much less trouble  than trying to match up small stand mounts and subs.

15 X 20 isn’t a small space. Maybe some moderate sized floor standers and a sub. ATC SCM40’s and an ATC C1SUB MK2. About 11K

End goal, the best 2 channel I can get.

In that price range ... Borresen X-1. $5500  High end speaker at a value price. Comes with special stands $7200 total. I would then call REL and have them advise you as to the best pairing. I’d push for a twin stack. ( 2 12" stacked)  ask them about this configuration.

Plenty loud for that size room! Better than floor standers by far.

Video review. (Notice he has a double stack in each corner of the room!!)

https://www.youtube.com/watch?v=Gi_LdATF634

maybe here >>

I think a crossover is the most important is a system with subs. Lots of digital preamps have subwoofer control. If you want to use analogue system sublime acoustics makes some very good ones. You really need to highpass the subs for best integration. 
 

https://sublimeacoustic.com