Funny you should say collect them all. I currently have 3 pairs of the Kestrels and have owned the Shearwater HRs and Kestrel 2s. I like the Kestrels the best.
I bought one pair of standard Kestrels with the intent of hot rodding them myself. I found the parts but haven't pulled the trigger yet. I did however convert them to biwire.
I'm really curious about your thoughts on the Kestrels vs the Merlins. Not a fair comparison when price is considered but still interesting.