I think Terry already answered this one pretty well, so no comments here...
under 4", eaither leafs or coils are easy to lift. Over 4", coils get a bit more complicated (long arms and what not), so if you are planning on +4", then defenetly leaf springs is the way to go because of simplicity.
This also leads more to a CJ or YJ... They will generally be cheaper than a TJ, but keep in mind that they will also generally be also in worse shape and have more miles. Just something to keep in mind...
Here, I have to say that the high output 4.0L is hard to beat... I have heard and seen nightmares adjusting carbs on older engines. Plus, if you plan on off camber situations, EFI will beat carb any day of the week. And dont think the sensors get damaged too easily; yes, they can break down, but mine have held up fairly well, and I do quite a bit of river fording here in Costa Rica...
That you can retrofit into a CJ...
So are you planning on using the 2.5" springs instead of the 2" ones? Also, which engine are you planning on getting? And again, make sure you find one without rust!
That's really not a bad idea, especially if you go with the YJ lift kit to use wider springs. As for the speakers, you can use tons of available speaker boxes. Some mount under the door, some mount in the wedge between the rear fender and the seat, some mount in the front under the dash, and, of course, we have the sound bars... My only advice would be to make it as simple as possible, as you are planning on running a bikini top (which makes stealing it quite easy!).