Sorry...disagree on the Trackmaster. Doesn't even come close to being the same league as almost anything else in the $500 range. The BG1 is a great suggestion, but after shipping from the UK it'll be way up over $500 won't it? The RNP is a great suggestion...I have one...but the SM7 needs a lot of gain, and if it's a quiet source the noise floor gets pretty high. Got any DIY skills? You could build a fantastic pre for way under $500...look
here.
Frank