Cedar is pretty soft, a 550XP with a 20"B&C should handle Cedar up to 30-32" wont be the fastest cutting ever, but should be fine for the Limited amount that you need to do.
OF COURSE, We are all going to Spend YOUR Money, and tell you that nothing less than a 395XP with a 36" B&C will do
A second saw is always nice to have, and with the 550XP, either the offered 288XP or if looking for New a 372XP would each be a Good choice with either 24 or 28" Bars.
If Nothing Else, get another Bar with matching chains to fit the 550XP, so if you, Er, Uhm WHEN you pinch a bar, you can at least remove the powerhead, mount up the second bar and "Rescue" cut out the stuck B&C.
A nice Little Top Handle saw would also get more use than you would expect.
A Top Handle, the 550XP you already have and a 70-90cc, with 24-28" B&C would make a Great 3 saw plan for someone that owns much wooded property,
If there is anything else that you need help spending your money on, I am Happy to Help
Doug