3 & 4 are a doddle to hit in the g range, don't dismiss them once the swing is solid
+1. I just recently dropped the 3i but the 4 is going nowhere and for a while I hit the 3i lovely off the tee, just wasn't getting any extra distance over the 4 off the turf. There's nothing wrong with the G15 sandwedge in so far as its designed to get you out, and it doesn't need to match your wedges unless you intend to use it as another gap. The G15 PW is 45*, so were you to get a 52 and 58 this would be almost perfect 6 degree gapping. The 54 sandwedge can stay in the bag if all you're going to do is play out of the sand with it, obviously if you play it from distance then going 45, 50, 54, 58 will give you 4 degrees.
Also - no need to spend the earth on new vokeys, there are lots of good wedges around, cleveland, MD, and your set can be picked up for price of one new one if you hit the bay with a little patience. Good condition red logo Vokey should be around £35, in comparison to many clubs they don't break the bank. I know what you're syaing as I'm not using my full set either but the G15s will hold reasonable resale value for a while yet so don't despair!
