[Tim]

Comparing the specs on the antennas mentioned:

CS600
2.3 dBd VHF Low
5.5 dBd VHF Hi

Clearstream 2
8.1 dBd UHF (converted from manufacturers stated 10.2 dBi)

C290
2.8 dBd VHF Low
6.0 dBd VHF Hi
7.9 dBd UHF

C490
5.0 dBd VHF Low
8.8 dBd VHF Hi
9.3 dBd UHF

The C290 is pretty much the equivalent of the CS600/Clearstream 2 you are using now.

The C490 has about a 3dB gain over your CS600 on VHF Low and Hi which is about a 2x power gain. It has 1.4 dB gain over your Clearstream 2 which is about 1.4x power gain on UHF.

The C490 is probably the minimum upgrade you could make to see any difference in the weakest stations.