I spoke to someone who has the Velocity on their system. He noted the problem with heat transfer. It was quite apparent to him, after upgrading to the T4. It created a very real/evident heat problem. It is just to what degree. And as you mentioned, room temp, etc., could be a contributing factor. He had to install a chiller.
His tank is a 75 gallon.
The cooling down while going through the pipes would depend on the type of plumbing and also the distance as well as the velocity. Do not assume that the heat would dissipate prior to reaching the tank.
I appreciate the assumption that it should not be a problem, believe me..... I have my eye on this pump. I'd like nothing better than to not have to worry about any heat transfer problems, etc..