Cable connections to an old receiver?

I'm setting up my first "real" stereo system and I'm wondering about the connection between my speaker cables and my receiver. I've got an old marantz that has the little boxes with holes in them and then a lever that you push down when you put the wire in the hole and then the spring pushes the lever back up to hold the wire in place (I'm sure this has a specific name but I have no idea what it is). When I ordered my cables, I described my situation to the cable maker and he suggested that for the best sound I should just use bare wires or he could sodder the ends (no spades or banana plugs). I chose to have him sodder the ends so that I wouldn't have the upkeep of bare wires. When I finally hooked up my speakers and cables last night, everything seemed to work fine, but the connections to the receiver seem less than totally stable and tight. I'm wondering if maybe I'm losing some sound due to a flimsy connection. Should I make a change? Is it fine how it is and it's just going to be a little loose? Suggestions?