Hi Forum readers!

I have a HTPC (but not deticated - occasional gaming and some tinkering with stuff) setup (OS is Linux / Gentoo) and I'm going to upgrade the CPU (and add 2-4 GBs of RAM). Energy-Power -efficacy is important, because of NOISE. There's just one problem: I can't choose which CPU to upgrade to

Currently it is running on AMD X2 4850e. The temperatures are VERY good on this 45W processor with the aforementioned exhaust fans just next to the Nexus Ninja Mini, even with full load it never gets above 50C (in the summer maybe just there - now that the sun isn't heating this apartment to the 32C ambient temperature, I really need to work getting the cores to 46C).

I have two processors currently in mind (that are available here):

AMD Phenom II X4 910e (2.6GHz, @65W TDP)
AMD Phenom II X6 1055T (2.8GHz, @95W TDP)

The price difference is negligible. I think that with the current cooling solution I'd have no problems cooling a 65W processor, but with a 95W TDP processor, I might run into problems. But, I read one can LOWER the multiplier on a non-BE Phenom II - so, if the cooling is insufficient, I could lower the multiplier on the X6 so that I'd run (when running at maximum speed) on 2.6GHz? If that is the case, I'd go for the extra two cores - or maybe even a 125W Phenom processor?!??

So, any experience with underclocking / undervolting Phenom II's? Is there a lot of TDP to gain, say, undervolting the aforementioned 1055T? Or a 125W one (either a X6 or a higher speed X4)? Do these new processors have any stability issues when undervolting / underclocking?