HiFi is awesome but yes the low end isn't the best around, very fast and is excellent at everything. My 12m HiFi typically starts working in around 14knots for me (75kg) and in this i can have a ball. But what the Hifis lack in low end more than makes up for in the high end, I am comfortable in 25knots and have taken it past this on a few occasions. If you are going to start freestyle/wakestyle stuff then definetly stick with these.
What size Hifi are you using at the moment? I have a hardly used 12m for sale...