With the C250 you have 2 choices- water ballast (WB) or wing keel (WK). Both have advantages and disadvantages. If you are set on trailering, the WB is the better choice, however even it is a heavy load. By the time you have trailer, boat, and equipment you are talking in the neighborhood of 10,000 pounds. If you don't have a tow vehicle capable of that, you'll need to figure that into your budget.
Not to disuade you, but rigging one is also not a trivial exercise. It CAN be done by a single person, but not without some effort. Friends of mine who have it down to an art can get it rigged and launched in about 2 hours and retrieved and de-rigged in about 1 and half hours. If you are doing it once in the spring, and then again in the fall and otherwise keeping it on a mooring or in a slip it doesn't really detract from taking off sailing on a whim. If you have to do it EVERY time you want to sail it can get real old real quick.
Both the WB and the WB are very stable boats, and easy to single hand without many, if any, modifications.
The WK and the WB trade off ease of trailing with headroom. The WK has roughly 9 " more head room than the WB.
Both boats are very customizable- and perhaps one of the biggest advantages is you can actually buy one, and still have funds to trick it out like you want. The basic boat is rather bare, but very functional and can be sailed away as is- so you need not try to do your customizations all in one season. I've been adapting mine for almost 5 years now

, and have some "before" as it came from the factory and "after" (i.e. now) pictures on my website (
http://www.markhartong.net) that can give you just one idea of what you can do. You really are only limited by your imagination!
While you can always go "bigger", I think that the C250, and its older sister the C25 really are the ideal tradeoff of complexity and cost.
I'd strongly recommend that you become active over on the Catalina 25 250 website (
http://www.catalina-capri-25s.org). They are a friendly bunch, and I'm sure that between the active members on the forums, plus the forum archives, you can find answers to almost any question about either type of 250 you could think of.