Hi Melanie,
First of all, welcome to BPO!
I think it is a great idea for you to switch foods. Vet's always recommend science diet, eukanuba, or IVD because they actually sell them. But there are SO many higher quality foods that are actually way better for you dog and cheaper at the same time. I was just looked up IVD and saw that it's $80 for a 35lb bag - thats insane, expecially considering it's made by royal canin so I know the ingredients aren't the highest quality. The only reason vets recommend IVD is that it is what they sell for allergy foods. There are actually tons of allergy friendly foods on the market, most of which are significantly less expensice and you can get at small pet stores. Do you have an especially for pets near you? They have the best selection (they have 6 locations all here in mass and I see you are from mass too). Petco and petsmart don't have the best foods, but they are deffinately better than the grocery store so if you can't find a small pet store that carries better foods they have a few good choices.
You deffinately want to stick to a high quality food - even though they seem more expensive, if you get a good one with quality ingredients, your dog will eat less than he does now, and deffinately less than a grocery store brand, so it actually works out to be cheaper. If you have to go to petco, I'd say dick van paten's natural balance duck formula is your best way to go, since they are one of the highest quality ones they sell at petco and the duck and potato is hypoallergenic (and we know your dog isn't allergic to duck or potatoe if he's doing fine on his current food). Another one I would suggest trying is wellness simple solutions duck & rice - it's relatively modestly priced and only has 5 key ingredients so its good for dogs with sensitive tummies. (here's the link to the wellness site:
http://www.wellnesspetfood.com/dog_wellness_simple_food_solutions_duck.html ). Also, it might be ok to try a different protein since it might very well be the grains that upset him (hence potato is good on his tummy). There are a lot of good grain free foods now adays - some that come to mind are canidae, wellness core, evo, nature's variety, artemis, orijen, and fromm
I recently lost my saint Zoey, who had irritable bowel. We tried a bunch of different foods - some of the foods she did best on were wellness, merrick, and canidea, so you might want to look at those. They're moderately priced too - wellness and canidea are $30-$40 for a big bag...
Where in Mass are you? Did Jasper get his surgery at tufts (they are awesome)? Also, where did you get Jasper if you don't mind my asking? The reason I am asking is that I am also from Mass and I am wondering if Jasper might have come from the same breeder as my Zoey