Help!!! Any info appreciated!

Hey guys! New to the site and have read a lot of great info.....need a little more help! I'm planning on buying a new board as a bday gift for my fiancé ( I know, risky) however I have done a lot of homework. He and a couple other guys that go out with us all summer learned on a hand me down 4'9 hyperlite. They're just getting comfortable letting go of the rope so still mostly in beginner stage I guess. The guys are between 5'9 and 6'0 and all in 170-180lb range. We have Moomba and are planning to add a sac this summer for a bigger wake. Nose diving seems to be the biggest issue for them and sometimes keeping up with the wake. I spoke with a very knowledgable guy yesterday at our local water sports store and I am leaning towards the 2013 Ronix Koal 5' for a little more surface area and rocker and its also super light weight.....any info or suggestions are GREATLY appreciated, Thanks!