Sounds and looks do-able. 2.25 pipe should be fine, seeing how other 4.6-5.0 liter motors usually run 2.25 dual exhaust. I would try to incorporate an "X" pipe into the mix if at all possible. Or as suggested (Adamag25) in another post, a dual in/out muffler, which will help with the "scavaging" of the exhaust. To make things easier, not as "cool", but have the exhaust exit the same side of the XK. I actually like the look of the stock tailpipe, where it really does not show, giving a "clean" look. I may have mine done around X-mas when $$ gets better.
'06 White Sport:4x4,4.7L, K&N CAI,Flowtech Terminator muffler,Flashpaq,OME HD lift,RRO UCA,20" GF-X wheels 275/55-20 Nitto Terra Grappler tires,rear grab handles,tinted tails,front hooks.