SSR 2.5 is a fine product. I'm not sure you'll ever need 64oz of the stuff, but that's certainly a great price.
The SSR line works great on GM's moderately hard clear coat. 2.5, depending on your pad, will cut through the imperfections just fine, but you may need to make another pass with SSR 1 to remove light hazing left behind by the 2.5.
I'm an old time LC user, and for this I'd use an orange pad with the 2.5, and a white pad with the 1. If you're looking for a one-step polishing effort, I'd probably recommend going with SSR 2 and an orange pad.
A little FWIW.... I find that 2.5 dusts quite a bit, and I always found myself wishing for a little more working time when using it. The remedy...add a little bit of SSR 1 - maybe a 75/25 mix of 2.5/1 - and that will increase your working time and will finish down a little better.
Finally...and I'll shut up soon, I promise. I LOVE Poorboy's - great folks, great products. I'm just one of those guys who discovered the Meguiars 105/205 combo, and I haven't looked back since. Not trying to sway you, just offering my experience. Unless the finish is in really tough shape, the 105/orange > 205/white formula is perfect for this application.