Quad Options..

Happy Holidays everybody!
I have a decision to make that I think you guys will be able to help me out with. I have recently put my 440ex for sale so I can save up for a 450r or YFZ450. I love the way my 440 handles jumps and lands. I really feel comfortable on it and I hate to see it go. When I got it it had a great suspension set-up already and to many other parts here and there to list. I cant decide if I should sell to get a 450 (6g's) or save up to get a crf450 or yz426 enginr for 2g's and have my frame modified to fit the engine. Will a 400ex with one of these engine and a great suspension be as competitive as a newer 450? How much money would it take to get the engine to fit correctly in the frame. I have a friend with a fab shop so I'm sure I can cut cost there. What do you guys think?