Hi, I used a larger AMD Heatpipe Heatsink with my FX-6300. It's the same cooler that comes with a Phenom II X6 1100T. So, yes they are interchangeable. I thought the stock HSF was a little small myself. And, I already had the other cooler, so...
Good luck. hope this helps!
I run an All-AMD Household: Main PC - Gigabyte GA-970A-D3 - AMD FX-6300 BE - 8GB DDR3-1600 - HD6870 - 2x WD 500GB Blue - WD 1TB Black - 2x LG DVDRW - Xonar DG - CM 500W PSU - Antec 900 - Logitech G5 - Logitech USB Media KB - AOC 23" LCD - Creative Inspire 2.1 - Windows 7 Ultimate 64Bit - Other Machines: PII X2 255 BE (4 Cores) + HD6870, 3x PII X6 1100T BE + HD6870, HTPC AthlonII X4 630 + HD6450