I have been able to pretty much run all my Phenom II's @ 4.0Ghz.I have never had to up any voltages. All have been done strictly using the multiplyer and have been 100% stable.Temps have never been an issue this way.
I find that 4.0Ghz is the sweet spot with these chips.Any gains over that is really negligible.
Dont forget to always do your O/C only from the BIOS!
AMD Phenom II 1100t @4.0Ghz /Asus sabertooth 990fx/2x Gigabyte 3G 7950's in crossfire/500G samsung 840 ssd/16G G-Skill Ripjaw 1600/2-samsung 24" monitors 1920X1200/Corsair AX1200W psu/W7 pro 64,G19 keyboard,Roccat kone pure mouse,Cooler master HAF932,Corsair H100i water cooler,Zalman ram cooler.Sound Blaster X-Fi Titanium Fatal1ty Champion Series,Logitech Z5500 speakers,Roccat Kave 5.1 headset.