Should I?

[xneox]

I'll try to keep this as short & sweet as possible...maybe even post as a poll.

My current setup is all entry-level JBL within the same series - small bookshelf as mains, smaller as surrounds, and matching dedicated center.

Power is Pioneer VSX517 (110w/ch rating).

I've got about $400-$500 to spend, and new speakers is an option.

Newegg is having crazy deals on Polk Monitor series speakers. As much as I'd love to go balls out, I can't. I'd even love to do 40s, but I can't fit them in my current setup (check gallery for why).

Would it be worth it to buy three pairs of Monitor 30s at the current sale price, and run them as the 5 in my 5.1 (with one spare)? Would that be an upgrade for me?

With regard to the center channel specifically, would one Monitor 30 be an improvement over the center I have now (taking into account the MTM issue I'd be eliminating)?

Lastly, if needed, can I run this particular speaker on its side? The tweeter doesn't seem to have any funky baffles (like my JBLs), so maybe it would be ok...?

Thanks in advance for the advice. There are definitely other upgrade options (like tossing the 2550 in favor of a Panny BD85), so no love lost if the Polks would be a lateral move.