BTW because I am an aspergers type I made a spreadsheet with enchanter gear. These are my stat weights:
Int: 1 / Cha: 5 / Sta: 2.4 / Str: 0.5 Agi: 0.8
HP: 1 Mana: 0.15 / AC: 3
MR: 1.5 / CR: 1.5 / FR: 0.8 / PR: 1 / DR: 1
i.e. a piece of gear's 'Loraen Score' is the dot product of that vector with its stat vector.
So for example I wear the Insignia Protector (135) over the Crude Stein (99) and the BS Electrum earring (45) over the opalline earring (31).
Let me add that you can see my gear setup on the magelo:
http://wiki.project1999.org/Magelo_Blue:Loraen
Suppose I were to go for 255CHA. Currently my guy has 219 with the buff, so I'd need 36 more. So lets say I swapped out two BS earrings for opalline earrings (+10), the Elliptical Veil for the Incandescent mask (+4), the IP for the Crude Stein (+10), and the Granite Bracer for the 7 Cha bracer (7), and the wedding ring for the 7CHA one (7). Thats a total of 38 which gets me 2 over the cap. Meanwhile I'm losing ~150HP and ~30AC. That's probably almost an entire attack round. And I have the advantage of having pretty good gear; you're going to have to make even bigger sacrifices if your gear is worse. Meanwhile under the most optimistic assumptions I'll be getting 227/210 = 8% longer charms. If Charisma is softcapped at 4 or 5 to 1, its even less.