I have an FMR audio RNP and I really like it. I have it racked with the RNC. I haven't tried other mic pres, but the RNP does well for me. I like that it is 2 channel, it allows me to run my 2 small diaphram condensors for recording an acoustic guitar. Also I like to use 2 mics on a guitar cab and blend to taste. So you might want to consider a dual mic preamp for that.
What I found when looking for mic pres, was that there were 3 classes. The $250 and under, the around $500 and the $1000+. I went with the around $500, hoping to get something decent and I feel I did.
I have used the mic pres in my allen and heath mixer, but I only use those when recording drums as I need 7 inputs.