urrently, I have a NAD 2100 amp in my listening "man cave"

I have the opportunity to pick up either a NAD 2200 or a 2400THX. The specs on the 2200 and 2400 are identical in the owner's manuals.

Would I notice a drastic change if I were to pick one of these other amps up as compared to the 2100?

I'm fairly happy with the sound, but the bass seems a bit thin? Yes, musical, somewhat tight and deep, but doesn't have that extra punch behind it when listening to rock albums. Would more power help or is the 2100 good enough and I should look at different areas (ie. my cheap CD player)? I also have my Computer hooked into an auxillary input with the same results.

Also, is there a preference between the NAD 2200 and 2400?