I also don't buy big-ticket items lightly. If saving hundreds is a possibility, then there are also way way more considerations, and I'll probably end up targeting a particular model of a particular brand, then I'll search for the best price. Your solution may work for that, but so does Google and just going to each retailer's website manually.
With big ticket purchases, convenience isn't really a factor in my purchase decision. To me your product is a solution in search of a problem. I hope I'm wrong.
I've been surprised the extent to which Amazon's achieved voluntary lock-in for me. Amazon's good-enough in my spot-check price comparisons, and instantaneous with zero marginal-cost shipping, that they're now my default place to search for many products.
Find a niche to live in. Taking on Amazon directly is probably trouble.