100W/sq.ft. is great, but the bottom line is 50W/sq.ft.
If you can get above that, you'll be 'in the zone'.
A smaller room should help a lot.

Weedhound, your math is wrong.
10x10 is 100 sq.ft.
1000W would only be 10W/sq.ft.

Baldyhippy...
Your 6x3 room is 18 sq.ft.
so you need at least 900W, so your 1000W would put you in 'the zone'.