Thanks for the advice so far.
I am not really set on PSB, and I've only heard the older Titans (v.2 or v.3, I think). I liked them, but they didn't compare to the Monitor Audio Silver xi stuff or the Paradigm Studio stuff, and nowhere near Snell. I've heard DefTech extensively as well, but was not into their over-bassy response curve (or so it sounded to me).
However, I like PSB so far because they seem good for the money, which is my main constraint. My dad is less hard to please in the quality department, so even if the PSB's are only "okay," then they're still probably more than he is expecting. However, I am constantly looking for the best deal. Right now there's an auction for some NHT Super 1's/2's with a center and a sub for decently cheap, but I remember not liking what I hear from NHT's (though the memory is vague in my mind).
I am trying to figure out just what I'm going to need to fill this large room since I have a feeling that bookshelf speakers and a sub won't fill it properly, if you know what I mean. I have a feeling I'll be missing part of the frequency spectrum. That's why I want towers, which is hard to work into my budget. Hence my continual reversion back to Monitor Audio, the brand that I personally own. I found out that the 3i's that I have far outperform the Alpha T's, which is disturbing. It makes me think that I might be able to get away with some of the following:
MA Silver 4i's for front
MA Silver 3i's for rear
MA Silver 10i for center
MA ASW110 for sub
replace the 4i's and sub with some 8i's.
Any ideas on what will be required to fill this room with even sound? Loud is not as necessary as flat response, in fact loud is not even desired for the most part, but I find that some systems only sound good at loud levels. I want this to sound good at lower volumes, maybe up to medium, but I know my mom won't want to watch movies at a loud volume because she'll probably complain to my dad about a headache and he'll never get to enjoy the speakers.
As far as a source/receiver, I am also shopping. I was thinking about NAD (since that's what I have, and I really like, especially for the money), but I'm also considering HK, Denon and Marantz. I know it may sound silly, but I don't want to spend upwards of $300 for a receiver, especially since I'm probably going to go overbudget on speakers.
If you people have any recommendations on what kind of power I will realistically need to fill this room with sound at low to medium volumes, I'd appreciate that as well.