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Here's the thing: when you're first starting out in park, exactly what ski you have doesn't matter as much. Where you mount it and the length are far more important. You should go for something around 185-188cm and center mount it. Your carving performance will suffer very little compared to how much center mount will help in park.
Find something cheap in around that size and ride it til it breaks, which probably won't be too long, because you're kind of a big dude. During that year or two, you'll have time to figure out better how you ride and what sort of ski will suit that style.
Hope this helps!
If you really want to try a pair of twintips out, you should check out some stuff from surface skis. Some people don't like them because of durability issues but i've found them to be good. You can check their online store for closeout deals to find a cheaper ski. Or you could check out the 'Blanks,' their cheap park specific ski.
If you want to save some money buy a pair of used scott punishers. Thats what i did when I first started getting into park but wanted a ski that would slay everything else. It worked great, punishers are such an under rated ski.