Men! if signet channels are clear to you then you probably dont know clarity or lets begin with.. whats the size of your screen?
Do a recording of any Signet/STV channels with its best recording settings then with your Pc check MPC detail properties of the recorded material(TS format) check the Bit rate, Size(Width,Height), Display aspect ratio, Frame rate mode and Frame rate before you talk abt clarity.
by the way let me correct you.. Digital cable technology can allow many TV channels to occupy the frequency space that would normally be occupied by a single analog cable TV channel that means sayare and all other signet labeled channels are all under one frequency space with same decoding quality..
Clarity begins with the content before it gets decoded with a HDMI enabled receiver and even if u get 100% signal quality but the content isnt HD then no HD in the long run. ask yourself why DSTV has separate HD channels

I still insist No HD channel in FTA infact out of almost 200 channels only Bamba has less than 5 channels that ARE CLOSE to HD.. maybe MOA will do a better job than Signet, STV or PANG.. we still have a long way to go.. if you are viewing through CRT or 21"/< LCD/LED you may never get the difference

Thanks @D32 for the list. Does one get the other local channels like KTN, NTV, etc? They do not appear on the list...

As long as it works fine, why change? Besides, a stand-alone separate STB offers greater flexibility.