Replace Coax Cable or not?

I have Direct TV installed using the existing RG6 dual shield coax cable already in the walls. There are 4 RG6 coax cables rated at 2.2ghz from the dish to the basement where all of the room RG6 cables home run to.The RG6 cables that are already in the home are rated for only 1ghz. Will I get a better picture if the existing 1ghz cables are replaced with 2.2ghz cables? The picture is better with the satellite vs CATV but not as good as others I have seen with Direct TV.The HD channels vary depending on the programing.All other channels are always about the same.
I have 9 year old wire to my D* box and brand new wire to my Voom box. PQ is equal. Some stations look better than others .---Some HD looks more like SD while some SD looks closer to HD. It depends on the station or movie. One of the reasons for poor hd Q is they just up convert and THAT looks bad.Stuff shot in 1080i looks great--While stuff up-converted looks bad. I find there is a correllation between what the dvd looked like; and how it looks on your screen; as a sat. movie.
If it were me I woulda demanded they replaced all wires when installed unless it was a complex issue, I dont think it could hurt at all to increase those cables.
Perform an easy comparison experiment. Fabricate a equal-length 2.2G cable: the same length as one of your original 1G runs. Then temporary connect it; just run it across the floor or through a window, whatever. Switch the cables back & forth over a few days time for comparisons on all channels, especially the higher-frequencies.
finally a question I can answer as an expert. I used to install primestar dishes before i was a "cable guy". The first part is very understandable...there is no difference on and frequency up to 1 gig. The 1 gHz spec on the cable does not mean it can't carry higher frequencies, but there will be much higher attenuation at higher frequencies. This means that you will lose signal strength at high frequencies which must be compensated for by didital error correction in the receiver. this means instead of real information your box is using an algorithm like MP-4 to "guess" about missing information. Ultimately, like any digital algorithm, missing information leads to poorer quality. It depends how picky you are. I liked bob's experiment, which is to loose-lay THE SAME LENGTH of 2gig cable and compare picture. Length is important because a short cable always attenuates less than a longer cable, especially at high frequencies.