As far as what your motherboard supports, if it supports Core2Quad, it will support EVERY Core2-based CPU all the way up to the QX9770.
I see that you're now feeling the pain of having chosen socket 775 over socket AM2+ because Intel's products are ridiculously overpriced. If you want to upgrade to something more powerful and keep it around $200, I would recommend the following:
CPU - AMD Phenom II X6 1055T: $150
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103851
Motherboard - ASRock A770DE+: $61.55
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157226
Yes, the total is $211.55 but that's the best deal you're going to find out there. More importantly, you'll have a BRAND-NEW motherboard with a BRAND-NEW CPU that is designed specifically to handle highly-threaded applications like your multi-tracking music software. I mean, let's face it. Your Q8300 is slightly weaker than my Phenom II X4 940 Deneb so for this highly-threaded application, the Phenom II X6 1055T Thuban should be a significant increase in performance. I chose the A770DE+ because it supports DDR2 RAM which I'm guessing is what you use. If you use DDR3, then my recommendation would shift to the ASRock M3A770DE+ which is about the same price. You don't need to completely re-install your OS, a simple Windows repair will have it working with your new hardware (if it even needs that). I switched from a super high-end MSI K9A2 Platinum motherboard with the astonishing AMD 790FX northbridge to the rather lowly (by comaprison) ECS IC780GM-A with the AMD 770 northbridge and Windows 7 Ultimate x64 didn't bat an eyelid. Windows XP Pro did need a windows repair but all is well and I lost nothing. Here's another thing to think about. Had you chosen Phenom II X4 over Core2Quad, not only would you have paid less for a more powerful CPU, you would have paid less for a motherboard that only had USB 2.0 on it (instead of USB 1.0 and 2.0) and you'd be dropping that Phenom II X6 CPU in right now without even a second thought. Maybe choosing Intel wasn't a good idea.