Help me choose

I'm in the market for a 2 channel amp. I've been burned on Ebay buying used stuff before so I've been shopping for something new and I've found the two follow online bargains:

1) Parasound Halo A21 (125/channel) for $532(list $850)

2) ATI A1502 (150/channel) for $493(list$800)

My goal? I have a Denon 3805 powering 5 speakers, three of which are 4 ohms(Polk LSi 15's and LSI C). I'd like to take the strain of the LSI15's off the Denon while added more depth, bass, and soundstage while listening to 2 channel. When I heard the LSi15's demo'd in the shop there was a DRAMATIC difference between the 3805 (which sounded "nice") and a 140 RMS B&K (which sounded AWESOME).
I'd like to recreate that sound. That B&K is $900 new.

Both the ATI and the Parasound get great right ups. The ATI has more power for less money but the Parasound is a more well known and respected(true?) name.

Help me spend my money!
I would recommend buying a used McCormack DNA 0.5. It is a very good amp, 100W/ch. Then, as your budget allows, you can send it to SMC to get it upgraded by Steve McCormack. I have never heard any of the upgraded amps, but have read on several posts that they are awesome. I just thought that I would toss that out as a recommendation. BTW, I sold mine to move into tubes, and I'm much happier with a tube amp.
I would agree with above post.You can buy used here too,its a little different than ebay.....Bob
You'd never notice the power difference between those two amps. It takes double the power for a 3db level increase and 3db is just noticeable. That said I'd go with the Parasound not only because of the better reputation but because they are made well and are very good for the money. For the money you want to spend you could get a Parasound HCA 1500A here on Audiogon with 200wpc. I'd opt for that myself. Sound quality will be the same but if you like loud at all get the extra power.