Were I you, I would try a Mini. Be sure to load it up with memory. It can use the keyboard and monitor you have now and is a cheaper way to get the Mac experience. When you discover that it does everything you want it to, you can unload it on eBay for nearly what you paid for it and go with a high end iMac, like I did. Be sure to get it from Apple on their web store and max it out re memory and HD size. It won't need anything else. Mine is awesome and I expect to be able to use it for years with out being forced into an upgrade by a new OS, connectivity issues or software demands.
Lately a computer of mine had been hacked though it was secure and all, and ever since then it hasnt been working properly. and i have been wanting to get rid of it and purchase a new computer. ive been keeping an eye on a mac seeing how they can use both XP and their own OS X tiger. and im the kind of person that does media stuff and not alot of gaming. so would it be better to go with a mac such as the mini or macBook, or just stay with stuff like Dell, sony,hp and alienware