20's? As in 20' tow straps? 20' hi-lift handle?
If you want power out of your WJ you really picked the wrong engine. The 4.0 is good at doing what it already does and not much more. To get a noticable power gain out of it you'll need to stroke it. Google for 4.6 or 4.7L stroker kits for it.
The weight of your wheels do affect your shocks, but VERY minorly compared to weight on top of the axle. I wouldn't get new shocks based on that. MX-6 are nice (adjustable), so are Bilstein shocks.
If you're looking at getting speed/performance/handeling out of your Jeep I suggest heading over to the Speed Freaks section at www.jeepsunlimited.com
'04 WJ, 6" Clayton LA's, 242 SYE, 35" BFG MT KM2's, 4.56 gears, & D44a locked
'14 WK2 Limited w/5.7L, ORAI, & Tow Package