you can find a b18a1 (90-93 integra ls) motor for around $400-500 dollars. HOWEVER, when you go this route, you will have to keep in mind that you will need new motor mounts (~$300), shift linkage, b-series transmission, axles and halfshafts to match your b-series tranny, etc. the price starts to go up when you go from a d-series engine to the b-series. not to mention the fact that you will have to change out the headgasket, timing belt, and water pump on a swap...

anyways, go with the d15b from hmotorsonline. everyone that has one, loves theirs. it would be a direct swap (no new mounts, no new shift linkage, you could...although i'd recommend against it...use your stock transmission.)