I have a bit of experience with Head 18x20 frames....
For my game the best I have hit and I am lucky enough to own a matched pair is the Head i Radical MP L5 Made in Austria.
The only modification I made is 4" lead at 3/9 and TW leather grip. Perfection.
Can't disagree tho on the i Prestige MP (PT57E) brilliant frame!
Head YT Prestige MP(2) iPrestige MP(3)iRadical MP(4)tiRadical MP(PT630)paintjob
MG Radical MP,PS 85(2) Max 200G(2)PDR + many more in hiding