To me, the room size and listening tastes would dictate speaker selection, be it new or used regardless of budget. For example, B&W Nautilus 805s are fantastic but are probably overkill in a room that is 8' x 12'. Conversely, the Nautilus 801s are excellent but will probably perform poorly in a very large room.

It would be interesting to see two music only systems worth $5K each. The first one has alot of the money tied up in source components, wires, and amps. Speakers get $800 or less. The second has $4K tied up in speakers and under $1K in source equipment, etc. Both rooms would be identical.

In a system that does primarily HT, the percentage is more towards speakers and sub, often the price of the sub equaling or exceeding the price of the speakers.