To the OP - possibly a stupid question, but have you tried youtube? I've found many of the brands mentioned here has at least one demo or so, installed on a Monster. Some better than others, but a demo, nonetheless.
I've got a 2007 S2R with Sparks exhausts. http://www.spark.it/index.php/
They're not very well know - but are Italian, beautifully engineered and look pretty slick - black carbon barrels with chrome and aluminium.
Most importantly - I think they sound better than Termis - a deep, bassy, crackling roar - and they are just half the price installed.
I have the Arrow thunder exhaust in black on my 796. Deep sound (the DB killers comes out easily) and matches the flow of the bike. You can get them at IndySuperbike Store for less than $600. Great service, prompt delivery. Highly recommend them. Oh, it took 30 minutes to install them.