Yea there's really nothing you can do at that price to get more power. Performance timing belt kits will do nothing for your car except cost you money. If it makes you feel any better, there's not much you can do at ANY price to extract significant power from an N/A EJ 4 cylinder.
You could get some Delta reground cams (you have to send them cores to work with-either your cams or a spare set), which will only run you ~$220, but installation won't be cheap at all.
If you want a boost in PERCEIVED power, you could get aftermarket headers which will do hardly anything for performance, but will give you a bit of extra growl. The shop shouldn't charge too much to install them, but don't take my word for it.