Bondmanp, I feel so silly. For some reason it didn't occur to me that the phono preamp would, of course, be plugged into the Radio Shack. And yes, this would almost undoubtedly lack the resolution to make out much difference. Ugh.... So often the simple answers elude us (by which I mean ME).
Clockmeister, I will probably give my ADS preamp a go with my turntable before investing in a phono preamp, but if I like getting into vinyl I will definitely get a phono preamp. I already have some nice equipment and don't want to spend more. The way I see it, there really isn't any reason to spend 'x' number of dollars on a preamp with a built in phono stage when I can use my Citation 7.0, for example, and get a good phono preamp. The citation is an excellent analogs preamp already, so I'd have to spend a lot of better it.
BTW, thank you all for the other responses. I haven't bought anything, of course, but if I do I am leaning toward a Cambridge Audio 540p. My main reason is that it is cheap and gives me a way to take another step into vinyl while keeping my investment low. However, I'd gladly take opinions on this piece. For instance, would it really be worth going up to the 640p for someone still experimenting? Things like that.