Right now I'm kinda stuck with upgrades, I play mp1-3 archon for XP farming and I can do mp8 quite comfortably with CM for machine pieces and organs.
The obvious upgrade would be some Inna's pants, but I lose a lot of EHP with that also LOH.
I was thinking of getting a chant's force with Apoc and getting a mempo, but that is way over my 40m budget right now.
A mempo won't help you reach the next WW breakpoint. You need 83% IAS from gear with your 1.64 APS wand to get over 3.0 and 9% from mempo would put you at 81%. You either have to trade your nat's boots for legacy zuni for IAS or use the IAS slow time rune to hit the next breakpoint. Personally, I don't think it's worth it, but some really like 3.0 for ubers.
As for what to spend your money on, I have no idea. You can probably get a Nat's ring with all resist for under 40 mil (I got mine for 12 mil but it was a steal), but that's mostly just a sidegrade with a bit more EHP.
I'm in a similar spot as you, except I'm stuck at the 2.5 breakpoint and not sure if I want to go for 2.73 or just stay at 2.5. Going to 2.73 is going to be annoying for me, like how going for 3.0 is going to be annoying for you.
Well, it depends on what you want to do. As Loroese's tables and recent example calculations showed, you won't get the damage back - even if you run the full CMWW simulation including all odds. So you will definitely lose some DPS. However, your stunlock will be super stable and you'll proc CM like hell. In short: fights will take you longer, but everything will go more smoothly and be safer.
My general rule of thumb is: if everything's fine and I don't die or lose mobs too often, I don't increase APS - rather decrease it by putting on more damage gear (int, crit damage, and so on instead of IAS). You have to find your "APS sweet spot" for every combination of your EHP gear at the respective MP level. It's nice to have the possibility to push it to 3.00 in case you need to, but there's no general "no" or "yes it's worth it".
I'd say it's not worth it, except maybe for ubers if your group doesn't care much about your dps contribution. For solo farming it's not worth the dps loss, imo. Most people on the official forums are saying about the same thing.
dont take frostburns, you lose to much crit chance with it.
and what about innas pants?
He is not on a CMWW build, in fact, he doesn't even have the CM passive because he doesn't need the cooldown reduction at all. His Frostburns give him a flat 26% damage increase - you need to spend quite a bit on trifecta gloves to even come close to that.
And he already mentioned that Inna's will cost him a lot of EHP, especially if you're on limited budget. And for ubers, in 99% of the cases Blackthorne pants are better than Inna's pants.
Lol! I was trying a blizzard build for XP farming on MP0 that was why I had the frostburns. I do have some trifecta gloves with armor and MF for normal use. Right now I have 35m saved and some more stuff on the AH for sale.