Well, since your armor and amulet choices rule out hitting 120% IAS, I'd sock that ruby jewel of carnage. I really liked hitting 2 FPA strafe on my own WF strafer, so if you're willing to let go of that scarab you could go
- damage% of fervor in the bow [15%IAS + 20% IAS on bow = 35% IAS]
- M'avina's diadem + something of fervor [45% IAS]
- Highlord's / Cat's eye [20% IAS]
- Wasting of Demons, er. Laying of Hands [20% IAS]
- Total: 120%
With this setup creatures should be dead before amp has a chance to trigger, so you might not even miss Atma's amulet. That fortitude should of course never, ever leave your bowazon. Also, since you maxed penetrate, you could replace that fervor M'avina's with Nosferatu's coil + (ruby (res. fire)) fervor Andy's visage.
If you're running Baal with her, you should still keep atma's in your stash for the big boss.
Don't forget you can also replace Mavina's pot with a 1.07 Valk Wing for ultra make up style. (w 120 bp)
Also if you opt to go for the 80 IAS pb, you could even use Andy's Visage for some nice LL and after effects. That way you could even keep using ATMA's scabbard, and I think the final damage output would be far more in any case with the double (or 4x) damage from Amp. I vouch for 80!
In conclusion, the first jewel would be best in any case.
What about a Nef rune for the knockback (I'm assuming you're using it for a Pit Strafer)?
That's what I've seen on Strafer guides, quite a few seem to be in favour of knockback to keep critters away from you.
Two-Hand Damage: 35 To (241-547) (138-291 Avg)
Required Level: 73
Required Strength: 134
Required Dexterity: 167
Base Weapon Speed: 
+250% Enhanced Damage
+ (3.125 Per Character Level) 3-309 To Maximum Damage (Based On Character Level)
20% Increased Attack Speed
6-8% Mana Stolen Per Hit (varies)
Heal Stamina Plus 30%
+10 To Strength
+5 To Dexterity Knockback