Honestly, I put some slower fans in there since the stock Nidec BETAV TA450DC seemed to be pretty overkill.  I replaced the 3 front fans with Yate Loon D12SH-12 fans (~2200rpm) and added two 140mm fans to the back (Yate Loon D14SM-12).  My temps seem to be pretty close to what they were with the stock fans (maybe 2-3 degree difference at their hottest point), but the A2 is a lot quieter and uses about 50 watts less at the wall.

I'm sure if you had a bunch of them in a data center it wouldn't really matter and you'd want the extra airflow with the stock fans, but in a residential setting with just a few units these replacement fans seem to be pretty suitable.