How about some pickups? blow 1-2 hundred on p-90's (great for sg). And a monster instrument cable ( the best in my oppinion ) kills 1-1.5 hundred. Replacement speakers are a great improvement for killing small sums. Try celestion vintage 30's or something, $110 each. If you still have the stock tubes in that peavey you can improve the sound tremendously by investing in some new tubes, what kind depends on what you play. I am going to suggest a very different kind of accessory to you as well, check out perfectpitch.com, worth every penny. A hardshell case may be in order and if you don't practice with a metranome the recording studio will know.