Best bet is to sale your 2k. Most stores dont wanna give u shit. They will want your MPC plus cash. If your mpc is maxed out and has extras(8 outs, effect card...) then u looking at 600-650. You can usually find some cheap XL's on Ebay or either try craigslist.
A few shops I've heard from even if you have 8 outs and max memory on your classic want $250 on top of the mpc classic for a trade.Best bet is to do what was previously mentioned and just sell the classic and then look for a cheap xl.
yeah I was working on trading in my mp 2k classic for an XL. I really don't need to but it's more for convenience of just having those extra features but I don't really phukin need them. This dude on ebay will do trade ins he has a shop in New York his name is armens or something to that effect. He always has MPC's for sale new and used just do a search on ebay you'll find him. But like everybody said you'll still need to put up a couple hundred in additional to the trade.
Armen is a good dude. He is excdellent at fixing Mpc's and other gear. he installed my card reader when my zip kicked the bucket. sometimes he drives a hard bargin but he won't let you down with his work. he is even listed on akai's website call him (212) 563-4514