Mf also increases your chance to get rares.....I'm not sure where you are going with this.
Here's a drop calculator for ya:
http://diablo2.ingame.de/tips/calcs/dropcalc/
It works for both classic AND expansion.
From my experience, it is as close to dead on as you can get.
Back to the main topic.
Monsters with a higher mlvl will drop higher ilvl rares. This may or MAY not make them better, as some migh lvl mods tend to be rather useless.
That being said, I have found that aside from soloing chaos (which as a sorc in classic = suicide) your best bet is to do hell meph, andy, AND Duriel. On classic, hell duriel has THE best chance for dropping an soj, followed by hell Andy). Now while the fireball/meteor combo will own Andy time and time again, doing runs that fast will get you r/d, and I'm sure that isn't your intent.
I would go with a blizz sorc, with moderate mf. While more mf is allways better, there comes a point where you lose killing power and the ability to survive attacks that comes into play when you sacrifice too much.
My blizz sorc setup:
Current lvl: 81
Skill point setup:
Blizz:20
Mastery:20
Glacial Spike: 20
Ice Blast:20
Ice Bolt: 6
Telkenisis: 1
Warmth: 1 (any additional lvls and this will get increased, as blizz is doing enough damage)
Teleport: 1
Static field: 1
Frozen Armor: 1
Shiver Armor: 1
Gear:
Head: 44% Tarn
Body Armor: Twitch
Belt: Goldwrap
Gloves: 24 fr 18 cr 22 mf gloves
Boots: 20fr/w 39cr 36 lr 22 mf boots
Shield: 47 ward (I planned on using a 3 p diamond sock grim or bone, just never found and at this point, not worried about the extra 10 rez, I'm maxed on fr and lr, and cold is at 60. Andy dies to fast to worry about poison, that's what pots are for anyways).
Rings: 1 +15 str +12 dex 18 fr 17 lr rare ring, the other is a soj/nagel depending on my mood. I tend to like the extra skill and extra mana so I usually stick with the soj.
Amulet: +1 17 priz +38 mana +45 (or so) life 15mf ammy.
Weap: Shard
Stat placement: Str: enough for gear.
Dex: ditto
Vit: Rest
Energy: 100
When using an SOJ, she has 850 life, 540 or 550 mana (can't remember off the top of my head), does 2.5 k max dmg on blizzard with lvl 23 mastery.
Note: I recommend IF you are botting, you change the Tarn with a 3 sock p ruby helm for added life, and you REALLY need the soj for the added mana. If you can find a real good stacked sheild (30/20 grim or bone) with priz, and stacked cr/lr, pdiamond it instead of using a 3 pdiamond shield or ward. Otherwise use a pdiamond grim (if you have that much str) or a pdiamond bone.
Other popular choices are of course using a gull and a ptarn (150 mf just from there), and then making sure you have 2 fcr rings, fcr in your ammy, and mfists.