I've been looking around different websites at each companies different models in the price range you are looking for.
If it were me, I would personally wait and keep saving money - If you've got $120 now, save an extra 40 per month, then in 3 months you'd have $250 and could get a better unit... save another 3 months and you'd have closer to $400 saved and could get an awesome unit. I'm not sure how you fish during the cooler months, but I fish year round.
Anyways, for the $120 range, I'd go for the Eagle Cuda 242. It's got the best resolution for units in that range, a 4" screen, 200. I've fished with a budy who has one, and I was actually able to see the arches (fish) easily as well as the bottom composition.
Here's one I found on ebay for $89 with Free Shipping:
Eagle Cuda 242
AFTER I LOOKED IN THIS GUYS STORE, I FOUND THIS:
Lowrance X50 DS for $125 free shipping. I don't think I'd have a choice but to get this one.. heck, I would have bought it if I hadn't found the one I got