Looking for a flat top 20" with a2 hand guards . At least a 1 in 9 twist. Ill go with a 18" if it was a 1 in 7 twist . Most i can spend now is about 400 - 450
$400-450 won't get you much of anything in terms of quality, reliability, and accuracy. At that price point, you are stuck with bargain basement options like those you are already considering.
For just a pinch more (~$500-550), you can get into vastly better quality with options like RRA, Armalite, etc. and other like "commercial grade" uppers. RRA Standard 20" uppers are available right now for $513 + S&H from one source I know of off hand and $519.95 shipped from another (perhaps elsewhere too but in that range), and Armalite has a metric ton of 20" A4 uppers in stock and ready to roll out the door for $550.
As to MarkCO's comments...I have posted issues with Del-ton barrels and products in very recent past re: problems/quality/etc. I'm not going to rehash everything here, but long story short...you may or may NOT actually get a Wilson bbl from Del-ton as they have been open about moving SOME to Mossberg barrels, especially on their (cough, cough) lower end models (i.e. - THE 20" YOU ARE LOOKING AT). Furthermore, the fit/finish/quality of the work done on the blanks (regardless of who made the blanks) is less than stellar in my experience. They are "cheap" for a reason. If you want quality...YOU PAY FOR IT!!

If all you want this upper to do is put rounds downrange...the M1S and Del-ton options will do that, but they won't be doing it with any meaningful quality or accuracy in mind, at least not for the budget options you are considering now.
Knowing what you have in mind for the upper in question and the end goals you have with it might help this discussion along.