@ara777
Shady has a really amazing understanding of speakers and acoustics. I agree completely with his advice. Moreover, not being a trained professional acoustician, even I can tell you that treating your space willy-nilly, without measurements and a deeper understanding of what makes a room sound good, is akin to trying to pick a lock with a fresh watermelon. Maybe you get lucky....
The reflections we hear are also a part of the audio experience, and without some reflection, even the best gear can be rendered lackluster and impotent. Your space does present some very unique problems, and I can think of several ways to utilize the basement overall to better effect. Since you have already indicated, though, that you are tied to this specific setup in your home, then all we can do is try to guide you a little to achieve the best sound possible.
That said, having your LP up against a wall is a recipe for bad acoustics. Treating that wall and keeping the same seating would do no better imo. Trapping your speakers inside those short walls will create other issues... same as if you treat the walls on the side and front of that space.
Using (for examples sake) the CCB-8s from Hsu, you could pull those forward just a little, toe them in so they are crossing in front of your LP (time-intensity trading) where they are said to image insanely well, and maximize your listening experience without having to throw everything you don't spend on speakers at acoustic treatments.
Also to consider, perhaps, should be the JBL studio 5 series speakers... a favorite of many here. They go on sale for deep discounts quite regularly and you should be able to take advantage of that to build a high quality yet affordable system.
I know its hard to wait, once you get the urge to push ahead, but I think you need to take a little time and hopefully experiment with your choices, and get to audition some speakers before you buy.