51 _is_ better than 20.. it can do the search in one cycle most probably, where with 20 it'll usually take two or three at least. Anyway, when it locks in 10 seconds it is clearly good enough. But it depends a bit on location, and if it's a cold-start situation or not (where again more channels are good). However, 32 channels are probably more than good enough for most purposes - the sensitivity matters more. I paid in any case just $55 for my 51-channel Holux so I'm a happy camper.