To the OP: A sump is definately worth it! You should be able to find a good used overflow for around 20-40. Check the selling forums. makes it real easy, and they are very stable - I had one for around 6 years also.
IMO, the only valve of any kind that should be on either the return or the drain is after a 'T' in the plumbing, to control the amount of water that goes to each outlet. For your small setup, this is probably not needed at all. Just run both open.
Someone else said it, but make sure that the running water level in your sump is low enough so that when the power goes out, the amount of water that drains from the main tank to the sump will not over flow the sump. Having your in-tank return high up, obviously, will minimize this.
Good luck!