If it is set at 80hz that is good, you said you using the box with one sub and it is meant for 2 and it is a single chamber box. Once you get the other sub in it should sound good
Bought mine new at sports authority for 300 total which came with an Olympic bench press and 45 pound bar with 300 lbs of weight. also check your local craigslist.
I have 2 12 inch P1's and they are pretty loud. If you aren't looking for anything very loud but just something that is good for a daily driver I would reccomend you get some P1's. They come as the P1L-212 which is the 2 subs in the ported enclosure made by Rockford.
Do you think that you could get your hands on a Rockford Fosgate ported box that holds 2 12 inch P2's I know they sell it loaded with the subs, but I already have the subs, and I just need the box.