Well, I couldn't honestly say that I can't have just one boat that will do it all for me. Since I bass fish, striper fish, crappie fish and do other stuff out on the lake.
Ideally, I would want an 18 foot rig for bass fishing, with a 90 horse or so, were it an aluminum rig, or a 150 were it a glass rig. Would need to have livewells, and all the amenities needed in a tourney rig. Would also need to handle rougher water fairly well, so a glass rig is probably a better option here (Russ010 can tell you what an average summer day on Allatoona was. Many are worse than that day).
For striper fishing, I would want a large center console with tee top. Fairly open layout, aside from a bow deck to throw a cast net for bait from. Rod holders all over the place, a kicker motor for trolling, and a large bait tank. Hull shape to handle fairly rough water
For crappie fishing, I would probably want something fairly similar to what I have now. 15 - 16 feet, aluminum, rod holders etc. Layout would be slightly different than what I have now, but not much. And, it definitely would have power tilt and trim. Only thing is, there certainly wouldn't be carpet in this, as this would be the rig that I would use for a lot of the conservation projects I help with on the lake. It would get covered in mud from beaching to cut trees or when assisting the lake cleanup efforts etc. Also, this would be the electric only boat, when the outboard is taken off (tiller motor of course). Therefore, it would need a layout that could work with bass fishing, crappie fishing, and contain a bait tank for electric only striper fishing.
Now, were I doing the boat like the third one again, I could do it for under 4000 again, I am certain. Possibly closer to 3500.
When I made a ballpark price range for the center console I will be building, I think it came around 12000, if I searched well for everything. I could do it for 7 - 8 if I found a hull and trailer, and built from there.
That leaves me, what, 4000 - 4500 for a bass boat. If I searched for the right hull, I could probably do it. There is a 1985 20 foot Bullet with a 200 for sale locally for 1500. Needs a lot of sprucing up, but I could likely do that for 3 grand.
There ya go, those are my 3, that will serve me well, yet still stay under 20 grand.