If you have time, guinea pigs aren't too bad, they are just time consuming. They always need cleaning. I've stopped breeding them time and time again, then, I'll start up again, and can't wait to stop! I use rabbit food and Vitamin C preservative mixed in the water. Works out cheaper than guinea pig food... And, I give them timothy hay too, and what's left over from the greens I cut up for my herps...
As for hamsters, I use Mazuri 6F for them, and I also use sweet feed for horses, a 50/50 mix, has grain/corn/oats, covered in molasses. Kind of rounds out their diet...and it's cheap. I use probably 75% blocks, and 25% sweet feed....