I wouldn't automatically assume that the marantz amp is inadequate just because of the price though. If it has the power and a sound signature that you like then you're set.
A little while ago, a friend of mine saved an old Luxman integrated amp from the scrap bin for $20 (turns out it just had a blown fuse). We tried it vs a $2k integrated amp (which is very popular on head fi) with a couple of different pairs of speakers . All 3 of us preferred the old Luxman. Enjoyment is not necessarily proportional to price paid.
I am nobody and I don't pay full RRP for any A/V product. I didn't think anyone did. Generally if you're spending a chunk of money, all you have to do is ask for a discount and you should get at least something. If I spent a lot of money with my retailer and they sold me a Susvara for $5k instead of $6k, does that make my opinion worth less?