The hop-ups are usually not something that needs upgrading right away...I have the original and it is bang on accurate. Also I have seen a lot of posts here where people upgraded the hop-ups and regretted it.
If your shooting is fairly consistent then it is probaly fine. I HAVE heard of some krakens hop-up rubbers that are white, and they had some problems...but apparently the black ones do a lot better.
Shims and bushings, and maybe the sorbo piston pads offered on airsoftparts.ca would be a good first start, although the tight bore will help as well...and you already know about a better battery....happy upgrading!
