My two cents - the only thing you need is Advantage.
We used to have three dogs and one cat - and although now we only have one dog and one cat, we still continue to get into flea trouble a couple times a year. After spending a small fortune on yard, house and pet treatments, my vet recommended Advantage. I think it's a bit more expensive than Frontline. It works great! I think part of our problem was that three neighbors that surround us have dogs - so we just passed them around.
Anyway, at the first sign of flea, we drop the cat and the dog and the fleas are gone in a matter of days. I'm not sure how you feel about Frontline, but my vet said he puts Advantage on the top of his list because, unlike others, it doesn't prevent fleas from getting on your pet. The fleas jump on your pet and then they die. Other meds encourage fleas to stay off - hence breading and eating elsewhere.
Anyway - I've done lots of price searching and here's where we buy ours (I think they're in Canada, but we've purchased twice with no problems). Good luck!
www.petcarepoint.com