Xtherm for colder nights, Xlite for not so cold. I did have an Xtherm spring a very slow leak that I was not able to find, after about 3 years of use, sent it back to Thermarest and they sent me a brand-new one.
x2 on the Thermarest xTherm. It has a great R-value -- which can be used in both the summer and winter. You only need to buy one. In the summer you could go with a lighter bag, or shed sleep clothing if you were too warm.
A good pad is 1/2 the battle, especially in a floorless. I don't think you'll get too hot in the summer and you'll be glad you have it in the fall and winter. Thermarest has a great warranty program, too. Based in USA and a lot of their stuff is still made in USA.