Cat, small cabin, 100 mph, twins, newer, turn key, 100k. I'd have to recommend you start looking for a 26' to 28' cat with wackers. A pair of 496's will get you there (barely) if you have to have I/O's. I like the room that wackers give you inside the boat. I also hate crawling around the bilge. Eliminator or DCB would be a good start. If you don't have prior cat experience expect 5-6k/year for insurance. Even with experience, expect 4k. It doesn't sound bad, at first, but $500/month in addition to $3.50/gallon gas, etc. really makes 100 mph cat boating expensive! Be careful with your insurance company. You may get your ins. company to write it at first. Then, once it gets to underwriting, they will kick it back. Been there.
Good luck with your search. There are plenty of boats out there that fit this criteria.