AMD light gaming build - PS decision

I'm working on building an AMD build for light gaming. I mainly do wordsmithing along with moderate graphic & web design work on it. Main considerations are stability and reliability and good quality audio (for highly accurate voice recognition): plan on daily use for at least 2 yrs.

Just got the case via Newegg ShellShocker the other day: Coolmaster Storm Sniper (included a CM Storm Sentinel Z3RO G Mouse)

My next decision is the power supply.

(Planning on Asus M5A990FX mobo -- reviews have said it has very low audio distortion -- with AMD Phenom II quadcore; AM3+ down the road)

For now I'll just use the GT 8600 in my current machine: which will become an auxiliary / HTPC.. But down the road, I want to be able to upgrade to something like a GTS 450 down the road. (My gaming needs are quite modest but I am looking at StarCraft II -- I mainly play RTS games.)

After making my eyes bleed reading reviews for about a week, PSU I'm looking at: (Newegg links with prices: includes shipping, promo & rebates)

CORSAIR Enthusiast Series TX650 V2 650W => $62
XFX Core Edition PRO650W ==> $76
SeaSonic S12II 620 Bronze 620W ==> $80

I'm sure all of these have more watts than I really need, but I'd prefer not to be pushing a PS near its limits and stay fairly quiet.

Of course, I'd like a modular design but then I'd need to spend about 50% more to get the same high quailty. Besides, the Storm Sniper has lots of space to hide cables behind the mobo tray.

Thoughts about my 3 contenders? Are there others I've overlooked?