As someone who just got into the ultralight thing in the past couple of years... I sympathize. I just want to repeat things that other people have already mentioned, but with a different emphasis:
You will always be able to find something lighter than what you have. Always. You just have to decide what you are willing to carry, and what you are willing to spend to lighten. So, if the GPS is important to you, I say keep it. If you get heavily into the ultralight thing in the future and ounces start to really matter to you, then you can reconsider the GPS, or perhaps save a few ounces with a Garmin Geko or a GPS watch.
If you want to slim down quickly then the Big Three is the place to start, as mentioned:
#1 pack: I understand that you have found a pack with a suspension that you find comfortable, but there are lighter packs with decent suspensions out there. They aren't complex suspinsions mind you, but they are out there. Gossamer Gear makes light packs that at least have aluminum stays, for instance (save 20 ounces). Not all lightweight packs are suspensionless like the GoLite Jam2 (which happens to be one of my current packs). And, maybe years from now when you've gotten your pack weight WAY down the suspensionless packs won't be so uncomfortable. As a bonus, ultralight backpacks can be cheaper than many normal packs.
#2 tent: I sympathize with you regarding your wife's insistence on a nice big tent. (I won't get into my own spousal issues...) You can lose ounces cheaply by replacing your shelter with a tarp, as you mentioned, but a truly light bomber freestanding double-walled tent will (as you can imagine) cost you. They are out there- Big Sky International makes some neat ones- but they are financially painful. Good luck. Another option might be any of the 2-person designs by Tarptent, or similar. They are single-walled, and I'm not sure how your wife will feel about that, but they do have floors and mesh to keep the bugs out. You could save about a pound with one of these.
#3 sleeping bag: The sleeping system is the place where most lightweight fanatics drop serious cash. You mentioned that you covet a new bag. I say go for it- You're going to spend a lot on a nice bag anyway, so why not throw a fraction more $ at the problem, and get a light one. I have (painfully) made the transition to quilts, and I'm currently coveting one of the Nunatak Arc quilts for colder weather. 20 degrees, 20 ounces. (Roughly.) Gossamer Gear and some other companies make top-bags, if you just can't wrap your brain around the quilt thing.
Then, sit down with all your gear and ask yourself "What have I not used?" Anything that you can't remember using in the past year- sell it. I suspect that you might find that you haven't used all those clothes in a long time, barring special circumstances such as winter snow-camping, or whatever. But do you really need 1-pound mountaineering pants for hikes like this? I'm not one of those "don't carry more clothes than you can wear at once" fanatics, but I agree- you can lose a lot of the spare clothes. (I carry spare socks, for instance. I also tend to wear a short-sleeved base layer in warmer weather, and carry a backup long-sleeverd base layer in case it cools off. I guess I could wear both if i had too...)
I agree quite vehemently with the one comment made about your cooking setup- If all you do is boil water, wow, you can do that for a lot less weight than a JetBoil! Especially on trips less than a week, you can use a Caldera Cone or other alcohol or Esbit-style stove. If you use ethanol for fuel, you can drink it, too. (Alcohol stoves lose their weight advantage on longer trips, because the alcohol weighs more than isopropanol or other gases. There are several highly scientific articles about this issue on this website, if you want to search for them.) I suspect that the higher fuel efficiency of the JetBoil will only save weight for VERY long trips with no resupply stops, compared to a lightweight titanium gas stove.
And, don't let these guys fool you- the "you don't need a knife" thing is for the REAL fanatics. I think that any of the lighter multi-tools is a reasonable choice. I have a Leatherman Squirt. (Which I prefer to the Micra because the pliers come in handy for gear repairs, though I miss the tweezers sometimes.) But I agree that if you have one of these then the Spyderco is redundant, even though it is only 0.8 ounces.