I recently purchased and LFM-C and LFM-Plus.
Both were B Stock. The LFM plus B stock is currently $474 with free shipping, which is awfully close to your budget. Other than the subs being about an inch higher than they were listed in their descriptions (which affected where I could place them), I have been very pleased. I use them in one very large room for music only, with 2 LCR speakers driven by an RR2150. I'm waiting for a while before I post a review, but I can say that I'm very pleased with the subs.