12k is a good budget for a reasonable size second hand RIB or a cheaper smaller new one. Particularly as its coming to the end of the season when boat prices are traditionally depressed!
My thoughts are as ever with a second hand RIB focus on the engine in particular. On a second hand boat the engine is the key. Take that Tornado for example, good boat (assuming its in good condition) but if the engine is a carburretored V6 then effectively its worth no more than a couple of grand at the most. The new generation two and four strokes now really rule the roost simply because they are so much more fuel efficient. That 175hp will go great guns but will burn around 10gph+ at cruise. Believe me thats a lot of money in fuel.
So look for boat with a Ficht/Optimax/HPDI or 4 stroke engine. With 4 strokes that'll probably drive you towards a slightly smaller boat say 5.5-6m but thats a good size for a first RIB. (This is all IMHO of course.) Assume you are not in any huge hurry so take your time and look at (& hopefully test drive) a number of boats to get an idea of the market, condition of boats, etc.
Another of my particular bug bears is seating. Please, please if you want to do any serious Ribbing go for jockey seats rather than benches. Your back will thank you!
Have no knowledge of pro-sport RIBs personaly but have a suspicion that they might be similar / same design to BWM's. Not in itself a bad thing but check build quality. Sticking to one of the more well know names might be a sensible move. (Ribtec, Ribcraft, Redbay, Avon, Humber etc etc.)
As you know there is lots of advice and opinion on this forum. A trawl through previous topics should be rewarding!
Good luck and have fun,