Hello team (and your friendly mall ninjas, I guess =) )
A few things about the plates, I found a few sources (including a new one based in Canada) that may increase the choices we have here (I've PM'd Greentips to get his view on this).
Ref plates, there are LVL IV standalone at 7lb (Op Cut, MSA Paraclete) range, and even lower than that not at the $1000 mark (i.e. boron carbide specialty plates). The question is getting your hands on them legally. Plates need to be tested for the rounds you face; as GT said SS109 (M855/C77) will go right through poly plates while M193 will zip through many steel/ceramic plates that stop SS109...as for the newfangled SOST round...to be determined...hope you don't run into a guy that raided the USMC/SOF armoury.
GT, but blousing boots make the mall authorities look professional and keeps the ants and ankle-biters from sticking digits etc into their ankles!