I have been using my Mackie VLZ mixer for a few years and would like to get a preamp that is a step up from that...My price range is ~500. There are many mic pres in this range (grace 101, Summit 2BA-221, "The Brick", RNP etc.) and some of them are tube...Since my main vocal mic is a Rode NTK should I avoid a tube pre and go with something cleaner to bring out the NTK sound? or does that not matter much. Ideally I could get a stereo pre and use it for stereo guitar recording...but my main concern is recording vocals, bringing out the best in this mic AND getting something that is a noticeable step up from my mackie. I appreciate your help in advance and please recommend any other pres I am missing?