If you just want to ride it in a straight line super fast, the SeaDoo RXP is probably the ski for you. It's the 215hp Supercharged Intercooled 4 stroke that has some proven track record.
The RXP-X is faster and newer.
Stock a RXP is around 67-68mph (legit, not speedo). If anyone seriously tries to convince you their ski goes over 70, they've either dumped a lot of money into another ski besides an RXP (or the select few forced induction 4 strokes), or they've got an RXP like ski with minor mods.
If you really want to have fun and show off, get a stand up ski. Most people dont go back to riding a couch when they get on a standup