Heber, you may not have noticed that the OP is from Colorado (Freakinaye, it would be nice if you put that in your profile). (S)He _will_ need a 20-25 degree (accurately rated, which, as you know, most bags aren't) bag for summer--high in the Rockies it can and often does get below freezing any night of the summer. By late August-early September, it's down around 20-25* every clear night. For winter (s)he would need something that goes well below zero.

Freakinaye, I have heard several complaints that the REI Sub-Kilo, like many inexpensive bags, is more like a 30* bag than 20*. You might want to check gear reviews on http://www.backpackgeartest.org/ and other places before buying anything. If you're planning to invest in super-ultralight gear (most of which is super-super-expensive because of the high-tech lightweight fabrics like cuben), you might as well go for a Western Mountaineering bag, which is well worth the extra $$$. In your place, I'd spend my money there first and get a less-expensive (and adequately sized) tarp. Weight-wise, you'll undoubtedly save more with the better bag than you'll gain with the cheaper tarp. Properly cared-for, the better bag will last longer.

There are lots of excellent articles on gear on the home page of this website which, IMHO, is the best place to start. I got my base weight down to 14 lbs. by using the "27-lb, 7-day Gear List" article there, without sacrificing comfort or safety. A person who sleeps warm and is comfy with a thin pad could probably get closer to 10-12 lbs. base weight.

BPL has a forum which is free and the best place to ask specifically about the stuff BPL sells (which, judging from my own comparison shopping, is not necessarily the best nor the lightest and often not the best value for your $, so do shop around). It has a free section for Reader Reviews. It also has a section for people to respond to BPL's own reviews. Even though "official" BPL reviews require a subscription, you can get a pretty good idea of their general drift by reading responses to the reviews. A few of the folks on the BPL forums are pretty extreme about how light they can get. For me, having encountered horrific conditions many times while growing up in the Rockies, what some of them advocate is a bit scary.

Another good place to read up on gear is Mark Verber's Recommended Outdoor Gear. He is a regular poster on BPL, but not one of the extremists. He appears to keep up-to-date on new gear and update his website accordingly. He freely admits his biases (a good thing, so you know where he's coming from!) but covers a wide range of brands and also suggests less expensive alternatives for those on a budget. Even better, he gives lots and lots of links to manufacturers of lightweight gear.

My own take is that by the time you add together tarp plus bivy or ground cloth plus bug net, you have at least equalled and often exceeded the weight of the lighter weight tarptents, such as those made by Tarptent, Six Moon Designs and Gossamer Gear. That's especially true for me, because I need a bug-free space in my shelter for my 80-lb. dog, who is part of my "sleep system." Your Mileage, of course, May Vary.

I think the others here are correct; don't go too SUL too fast. You need lots of experience with something in between traditional (heavy) and SUL before finding yourself stuck in an August snowstorm and high winds at 11,000 ft. with inadequate gear.

The most important thing is to do a _lot_ of research before you invest in anything. You seem to be doing that, which is great! But you need to expand your sources to a lot more than BPL and REI. A good start is that you came here! Use the links in the "Portal" on this website (and shop with them if you can to support this site!) and also the links to manufacturers in the Verber website. Also, be prepared to order stuff and send it back if it isn't what you want (try it out in the living room and, if you have one, in your back yard). The extra freight charges are a small price to pay for getting exactly what suits you.

REI, for the most part, sells heavy traditional-type mass-market clothing and gear. If you're trying to lighten up, it is definitely not the place to go for most items. What they call "Ultralight" is definitely heavy! They don't carry two of the best brands around (for some things), Western Mountaineering and Montbell. As a high-volume retailer, they obviously cannot carry any of the outstanding lightweight gear made by a number of US "cottage manufacturers." Unless you find what you want on sale or with a 20% off coupon, much of what REI carries is less expensive elsewhere. I'm not saying don't shop there, but do take your scale (my local store hates me for that!) and comparison-shop online before you buy.