With all the gear we've used and tested in that price range, I think there's very few boxes on the market that are really worth the money in the $300-$600 range. I've been giving "mid-level" pres and channel strips shit for about the last year because we've found they really don't perform much better than some of the best inexpensive/budget gear [ MS-1b, DMP3, VTB-1 ] , and they don't touch the performance of the high-end gear. Here's some of the best choices, IMO:
Tampa: Reduced to around $300 in the last year or so. Single-channel clean channel strip with mic pre/DI/opto compressor/dig out. The only mid-level channel strip worth buying, IMO. And that's because it's three hundred bucks.
FMR RNP: Siightly colored two-channel pre/DI with a nice airy high-end.
The Brick: Good for a few tracks. Gets wholly if you use it as your only pre on all the tracks. I don't think it's that amazing, but it's worth it - I guess. It's the only real tube pre available in that price range, so I include it.
Grace 101: Transparent, transformerless DI/pre.
The 101 is not going to give your music enough "oomph" and energy. The Brick - like I said - I wouldn't use it as an only pre on all the tracks. That leaves the Tampa and the RNP. I think if you want a channel strip with an opto compressor you should seriously consider this. But I think your best option is the RNP. It's two channels, and a good pre for drum OH's if you ever need it for that. Good DI for bass. Just enough color to give your music a little bit of an edge on the recording. And you can later just spend another $175 for an RNC and have two channels of very good compression, too, between the RNP and your recorder.
That's where I'd recommend you spend your $.
My 2¢.