I agree with everything ChrisP said - but I guess my main point was about cost consideration as Roy is on a budget.
Cheap 8" = can't go as high as better designed 8" before cone breakup and beaming
Cheap 1" = can't go as low as better 1" without distorting and massively reduced power handling
Cheap 6.5" = can't go as low (for same design/materials as 8") but will be able to produce 1.5k-2.5k better and cross with cheap 1" better
Passive Crossovers = generally not as steep as active- increases problem with 8" and 1" drivers outlined above.
And while I completely agree that woofer cone area is definitely not the only factor involved in bass lowness and goodness - a smaller driver producing the same bass as a larger driver will require better design and better materials ie. - expensive. In addition a small woofer that can go low requires stiffer cone, larger gap, great suspension - this compromises the effective usable bandwidth (higher frequency extension) of the driver.
I know these are generalities but thats why the best (subjective I know) line array PA systems are still 4-way and the best full range Hi-Fi/Studio systems are at least 3-way - useable bandwidth before distortion.
I guess my main point for Roy is dont get cheap 8" monitors unless you can hear them and reference them against some thing you know is good (like ChrisP said - you need to know whats good).
In your price range - active or passive 6.5" or good quality second hand active 8" is my pick - as long as you listen to them first. Second hand is your friend. You may sacrifice some bass with the 6.5" but I believe this is a compromise you might have to consider. If you can stretch - Brand new HR824s are only $2000 a pair now because of Mk2 model coming soon. I haven't heard them but others have vouched for them
http://www.awave.com.au/product_info.php?products_id=2025
I wonder how the 8" Truths would sound if someone chucked a Morel MDT-33 tweet in them? They go pretty low with low distortion for a 1".
Peter