It is more than likely that your picture quality issues are directly related to your satellite dish and not your receivers. Dish alignment and multi-feed issues are the main reason I opt for individual dishes for each satellite and use a Dp-34 or similar switch. If you are not satisfied with the current quality then have a tech come out to realign the dish, verify the feed, and make sure the dish is grounded. Be sure that the new dish is not being masked, and consider replacing your outside RG-6 with quad shield RG-6. At issue is the fact that the receivers can sync on a less than optimum signal. Any multi-satellite dish not only has less gain but issues related to skew.
As to a signal level of 55, that is a bit low. If you are in the mainland you should definitely request realignment, consider dish relocation, or a higher gain dish. The solution to your quality issues I believe is a good tech with a quality meter.
Wix
He doesn't mention which satellite has 55 signal. If it is the 129, that is high end signal and you don't know what you're talking about. If it's the 119 or 110, then it all depends on what region he's in. Also, not everybody wants a three-dish system with the added cost of a DPP44