BenQ's 1640 is here now & with f/w updates, QSuite 2 (Solid Burn/OverSpeed)
is proving to be a good /possibly great drive.
Nec's 4550/4551 should be around in about 6 to 8 weeks, however f/w making anything like the best of this won't appear until the end of the year possibly even Jan 06. This is as a result of having to wait for 16X RAM certification which should happen in Dec 05. Nec's speed of releasing f/w is not that prolific either. Since 3540a came out only 1 f/w (although this is in its sixth edition). Whereas BenQ's 1640 has had 6 f/w releases. The difference being each change of Nec's has been so slight as not to warrant a new title. BenQ's f/w updates have been quite significant on the other hand.
If you want RAM & like the "feel" of Nec models it's probably best to wait till the new year. If not then BenQ is here now.