Ok so i was looking at buying one of these and want to know some that are good some to stay away from and also do tese all have issues with needing professional expensive calibration?

I would like one that actually has CFM on it so i didnt have to use a calc from FPM to cfm..

Extech CFM/CMM Thermo-Anemometer looks like a decent one but may need calibration , which ones do not? these things range from $50-600 buck all being basic with just wind speed all the way up to multi function.. is this the best way to get cfm at supply's and such so i can get total cfm for the house and balance the duct cfm output?

input on what you are using, have used and some good and bad on the ones out there?