Yes there is a way to keep your steering wheel controls. It is made by PAC and it is a steering wheel control adapter.
PAC SWI-JACK Steering wheel control interface for Alpine, Clarion, JVC, and Kenwood at Crutchfield.com for Alpine, Clarion, JVC, and Kenwood headunits or this one for Pioneer, Jensen, and Sony
PAC SWI-PS Steering wheel control interface for Pioneer, Jensen, and Sony at Crutchfield.com crutchfield is a bit high I got mine on ebay for about $40 but crutchfield will help you with setup and they also send you free wiring and trim pieces if you buy a headunit through them. Just make sure the headunit your looking at will work with steering wheel controls so that it can connect to the pac unit you buy. The pac unit just plugs in to the steering wheel control input on the new headunit you buy. You then wire the pac unit to keyed + power and ground and hook one wire I believe is red/yellow (double check me through its been awhile since I installed mine) under your steering column so that it can get the signal from the steering wheel controls. Then you program it to what steering wheel button controls what on the stereo. Sounds hard but the directions at pac's website make it pretty easy if you just go step by step. Works great in my 2001 WJ. You can keep the factory amp too. The wiring harness you will get to hook up your headunit will allow the factory amp to still function. But you may want to remove it and install a better amp if you plan to upgrade your speakers. The factory amp is pretty low on power. Have fun and good luck!