TheRedGoat -
First, let me preface this by saying that the above posts recommending buying an inexpensive, good condition, used police-style bullet resistant vest are right on the money. That is a good way to go. EBay has them for under $150.
Now for your PASGT Kevlar vest question. PASGT Kevlar vest panels are made of 13 layers of Kevlar29 ballistic fabric. NIJ IIA Concealable Kevlar vests are made from around 14-16 on average. So technically, the PASGT vest is comparable to a IIA vest in construction. Last spring I bought a couple cheap, used, beat up looking (but with good panels) PASGT vests (and a USGI K-Pot helmet) and took them to the range with me and some friends. We shot them up pretty good with a .22LR rifle, 9mm, .40 cal, and a .45. NONE of the rounds penetrated a panel, front or back at point blank range. A 9mm mind you, is one of the hardest handgun rounds for armor to stop. The high velocity and pointy shape lend themselves to good penetration. The 9mm I was using was 124gr NATO FMJ out of a Glock 17, so the velocity was most likely 1200+ FPS. According to NIJ, even a level II vest is only rated for a 9mm 124gr FMJ at 1175 FPS. Level IIA vests are down around 1080. So by rights, those bullets should be able to defeat a level II, let alone a IIA but can they? Doubtful.
The PASGT Kevlar vests in good shape are much better than nothing and have the advantage of covering much more areas of the torso than a concealable vest. Are they comparable to a level IIIA, III, or IV... nope. Will they protect you about as much as a IIA... probably. I'm quite sure it will stop a 12 guage hit by shot (not slugs). Also, don't underestimate a .22 LR. Because of their small cross-section and velocity, they can penetrate Kevlar better than you'd expect (better than a .45 easily), trust me.
The NIJ won't rate the PASGT vests because they are front opening and don't have 4"+ overlap. That is a requirement of NIJ testing. It wouldn't matter if the PASGT vests had 50 layers of Kevlar 129, they'd still be unrated by the NIJ.
Also, a level IV plate will stop a .30-06 AP or lesser round from point blank range. A level III plate will stop a 5.56mm ball or 7.62 NATO AP or lesser rounds.
Finally, the best advice is when it comes to gunfire, don't get in its way! (Benjamin is right about that). [:)]