Two scenarios....
1. Even if you bought his cabinets for $50.00 his crossovers have the wires trimmed all the way back (would need to add wire.) I have a set of 8a crossovers with the wires intact. 12" drivers go for an average of $300 a pair, Polygraph K's $300 a pair (sometimes more), Polydome K's $300 a pair, EMIT K's maybe $200 for all 4 if your lucky (sometimes more). That's $1,100 in parts excluding the cabinets or crossovers, see where I'm going with this?
2. Wait for a pair to come up locally for somewhere between $600 and $900 (depending on condition), save yourself the extra time, aggravation, hassle and expense.
We could vote on this for fun.