That's a nice midrange, but if he's using a coax, that won't give him any highs. Components cost more and need to be amplified externally to get anything worth listening to out of them.
The Alpines fabbio25 listed are good, but a bit more than Scoche speaker price range. The Type S is a better value. I ran the previous version of these:
http://www.crutchfield.com/p_500SPS610/ ... S-610.html
On my old DD and was happy with just HU power.
6.5 is the way to go if you can return the 5.25s. Otherwise, check out this guy:
http://www.ebay.com/itm/Nissan-300ZX-Fr ... 3a6b5f8acd
And see if he'll make you a set for a 5.25" driver.
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