Look at it from a practical standpoint -
Because you already have your MEI, you could start CFI'ing in November, and you'd have a good 6 months of flight instruction behind you by the time april rolls around. Let's say you get on with an 'average' flight school and manage to log 60 hours per month of flight time. let's say you make an average of $15/hr for the CFI gig - that's $5,400 for those 360 hours (you will likely bill more than 60 hours a month, however, as that doesn't include pre/post flight, ground, sim, etc.).
320 + 360 = 680 TT. Now, there are regionals that will hire you today to 700 hours (as long as you have 100 multi as well, or close to it). Piedmont, ASA, Colgan, and Commutair come to mind. These places (except Colgan) don't have a training contract, so you can use them to get to your regional of choice should you desire to not hang around.
Let's say you do PACE. You graduate in April after spending $12,000 - $14,000. You've effectively spent $17,400 to 19,400 because you didn't earn any money.
Now, let's saying doing PACE gets you to an airline, say, even 6 months faster (assuming you don't interview at an airline at 700 TT after instructing, and it takes you another 6 months to get called). Is it worth spending upwards of $20,000 for 6 months? If you can say honestly, yes, then do it.
If you have any questions on PACE or Farmington, PM me, I taught there for 12 months (Ab-initio and PACE).
It's a good program, but the PACE program was simply instated because there weren't enough ab-initio students enrolling. Ab-initio is a great program and opportunity, but doing PACE is just downright nuts, especially if you already have your instructor ratings.
~wheelsup