Tubescreamer with AVT150?

Hi all!! :Spin:

I read a lot about putting a tubescreamer in front of your amp, and I want to try this but which one should I buy? My current amp is a Marshall AVT 150 head, and I'm using the EQ effect of the boss-ME8 to boost/tighten the sound, would a tubescreamer be any better? I'm not to happy with my current sound , i'm planning to buy a Pod xt after hearing some sounds on this board, sounds really good!! (or a 5150 head)

Thanx!!