I'm in the market for a similar monitor, and unfortunately if you're looking for something sub-$400 your options are going to be slim or non-existent. The cheapest 27" / 1440p / 144hz / IPS monitor that I know of is this Acer XG270HU, which is $470 on Newegg at the moment. A couple of places (Fry's and Newegg I think) had the Asus MG278Q on sale for $399, but that monitor is a TN rather than IPS panel. The Benq XL2730Z that you mentioned is also a TN panel.
My recommendation (for a triple setup) would be to try to find one of the TN panel variants on sale. Unless you absolutely need the extreme viewing angles of the IPS, with proper calibration you can get the color quality of the TN pretty close to the IPS panel.
ive even looked at the korean monitors, same price range.... -.-
its looking more and more like the 40" Korean 4k's are the best value for money atm....wich are fine as I like the looks of them, but i was thinking more of Lansyndicate's 27" limit and I was wanting to try to go if things work out.