Downunder: If you have a resolving system and can afford the 302 get it! but the 501 is a bargain and can drive low impedences (my WP7's dip to 3.4ohm).
The 501's are that much better than the 201's especially for driving low impedances (still pretty amazing and I wouldn't have pick this as a weakness if I hadn't been comparing it to my Lamms!!!) The 501 to 302 is just as big of a leap with twice the powersupply capabilities! The build quality and the cool to the touch is amazing on the rowland amps.
Raquel: I have only once found my Lamms sound the slightest bit dark and that was comparing it to the excellent VTL Sigfrued 400 amp that has a sparkle on top in my opinion! I totally agree that system synergy is everything.. My rowland preamp sounds amazing with my Lamms! (Lamm doesn't make a remote controled preamp!)