When modifiying your Max I recommend the following order of doing the changes:
1) Handling and braking
2) Power upgrades (if wanted)
3) Appearance and comfort changes
The last two are interchangeable as are the first and last. 1 & 2 are not in my opinion. What good is more power if your bike handles awful and can't stop:confused2: First mods in my mind should be SS brake lines, Progressive fork springs, and new rear shocks if not done already.
As for cheap power upgrades, there really are no cheap ways to get power. You can add an full exhaust and a jet kit (highly recommend Sean Morley's Muscle jet kit) for around $1k, depending upon which exhaust you choose (they can range from ~$500-$1,500 depending upon what you buy). Used exhausts do come up here from time to time for good prices. Other than adding NOS you are not going to add any more power unless you crack the engine and do a big bore, which will run well into the thousands of dollars.
Hope this helps.