I recently went through the same process. I previously used an Ultra PSU that I got free after rebate a while back, but finally listened to all of those comments about the importance of the PSU and that a substantial investment in other parts was riding on it.
The first step is to use a calculator like the one at http://www.extreme.outervision.com/ (there is a free Lite version or it costs just $1.99 for the pro version that gives you the amperage needed as well). I ended up getting the Corsair 520HX from buy.com for $89 after a $10 rebate. It got top marks from silentpc: http://www.silentpcreview.com/article699-page1.html and has a very high efficiency rating. I can atest to the fact that it is extremely quiet and has modular cabling, which was a big plus. The only negative thing I can say about it (and this is being extremely picky), is that the cables with sata connectors only have two connectors on each, meaning that for my three hard drives I had to run two cables to that part of my case. From the manual, it appears that the 620w model has a cable with three connectors on it, which would have been more convenient.
That's a crap brand name. Actually, it's Newegg's own in-house "brand name".
Get the Corsair 450VX. It may "only" be a 450w PSU, but it can provide up to 396w (33 amps) on the 12v rails. That's just 24w (2 amps) less than that crap 600w Rosewill PSU. Plus the 450VX is made by a PSU manufacturer with one of the best track record for quality PSUs, Seasonic.