I'd imagine that the 2.0 is carbed...so putting in a 2.3 block that has been reringed and maybe over bored, then adding a roller cam head, ported and polished...with a longer duration cam could probably be done for less than $1,000...depending on where you have it done etc...
I did that to mine (without the over bore on the short block) and though I did not have it dyno tested it was definitely more powerful than the 2.0 with the stock setup...maybe 100 to 120 hp, but I have no idea.
Going in another direction you could probably get a 2.5 and plop that in and then go fuel injection...probably get the stock HP of around 117 or whatever it was rated at...and that would be almost 40 HP more than the stock 2.0 (if 80 HP was expected)...so you'd gain about 50% more power that way...for probably less than you'd spend reworking a 2.3...and they bolt right up to your transmission...
Only major problem with going to EFI is swapping out all the fuel lines, wiring, and gas tank...including adding the computer...and patching the wiring to the old dash...so it can mean quite a bit of work...
Probably why I just dropped in the 2.3 block and kept the carb setup...gets you from A to B but not very quickly...
Biggest bang would be to swap in a 4:10 rear end and maybe a 2.3 block...then get a roller cam head and have it reworked...and maybe add the longer duration cam...