I always found my 2.5 to be adequate. I haven't had to deal with Titan other than with the initial purchase, so I have no comments on their responsiveness.
If you've got over 200,000 miles on your engine, there are probably a lot of things you should replace for good measure while you've got the engine out. I think I listed what I replaced earlier, but things like motor mounts, radiator, water pump, exhaust manifold, hoses, clutch fan, belts, plugs/wires/cap/rotor, etc. Anything that wears or wears out (like motor mounts) I'd recommend replacing while it is right in front of you. So that'll add to the $1100 your mechanic quoted. My shop also ran the injectors through their cleaning machine. So that's why mine was like around $6,000 when all said and done.
The year prior my clutch went, so I had all new clutch stuff and the heavier flywheel installed. But if yours has 200,000-plus miles on it, now's the time to replace all that stuff.