Hey @Ari - @hikermor notes a couple of key things: car camping/backpacking (and continued use after this trip) as well as where in "the Rocky Mtns" you are going.

You also don't indicate whether you're a restless or side sleeper (and beyond that is TMI, so no worries).

If you are strictly car camping then you don't need to worry as much about bag weight. It comes down to whether you tend to sleep warmer (throwing blankets off) or colder (grabbing anything you can at 3:00 AM to keep warm). In either case, you'll do fine with a bag that is rated to about 15-20degF. There is a rating system that bags use and it has become fairly standardized in recent years, so you'll be getting about the same warmth regardless of the bag. And I'd say you can get a good synthetic-fill bag for a fair price (like under $200). There's plenty of options on the website here.

That being said, here's a couple of other considerations:

  • Side sleepers tend to sleep more comfortably in "spoon" bags as opposed to standard rectangular or mummy-type bags.
  • Both Nemo and now Kelty have good options here.
  • You will probably be more comfortable sleeping with your regular pillow.
  • You will probably want a comfortable beanie (like a 250-weight Smartwool one) if you don't want to wake up in the middle of the night cold

If you ever plan on carrying your bag further, then you may want to consider spending another $100-150 to get a good down bag. It's much lighter and packs more tightly so you can easily get it into your backpack. It also keeps you warmer (usually). The "down" side (can't resist the pun) is that the down does not dry out quickly if it gets wet, while a synthetic bag can usually keep you warm even if it gets wet.

If you are one of those folks who likes everything to fit together, check out some of the BigAgnes products. Many of their bags have an integrated sleeve that's designed to hold a sleeping pad (so you are far less likely to roll off the pad during the night). And there are plenty of pads that you can get which could fit that sleeve.

Again, though, the choice of pad is driven by whether you're car-camping (tenting) or backpacking.

So if you give us a bit of an idea of what your plans are, you'll probably get better answers than these. But either way, enjoy your trip!