I didn't realize that the Ghost is that light! If your current pack is 36 oz., you are not going to save enough by switching to the SMD Starlite--$200 to save 6 oz. ($33/oz.!) is probably not worthwhile. Your Ghost is probably more valuable, considering that lots of folks are still trying to find one! Ditto the 30 oz. tent unless you switch to the pricey Gossamer Gear The One or equally pricey Z Packs Hexamid or (which may or may not be less pricey) a tarp/bivy combo that is no more than a pound. You can save some weight from the Downmat in warmer weather (the Downmat is so much warmer that I'd stick with it in below-freezing weather), but again the price per ounce savings of a replacement--especially the NeoAir--may be unrealistic. Certainly your sleeping bag is as light as it can get unless you go to a quilt or a less warm bag! (Again, the price per ounce savings are probably not worth it.) Your Big 3 or 4 (considering that you, like me, need a comfortable sleeping mat!) are very much within reason.

I suspect that going after other items than the Big 3 or 4--the lightest possible, avoiding duplication (except socks), multiple use gear if at all possible--may be a better way to go. If you don't already have a computer spreadsheet with every item weighed, set one up (it's also a useful pre-trip checklist!). After every trip, remove items you didn't use (except for obvious items like rain gear after a trip of all sunny days). Do you repackage items like sunscreen and bug dope into tiny bottles so you take just enough for the trip? That can be a significant weight saving over taking partially full--or full--larger containers. Replacing fleece (warm but heavy and bulky) with a puffy jacket like the Montbell Thermawrap (watch for sales) can help, too.

Posting your entire gear list with weights would undoubtedly give us some more ideas for weight savings. Be sure to include items worn or carried (not in your pack) as well. My biggest weight savings in the past 2 years have been in reducing the weight of my footwear and trekking poles, which are not part of pack weight but are still part of the total burden on my feet and knees!