To be honest I think you would be very happy with any of the subs being mentioned as the differences are really only noticeable when A/B'd, as long as the driver sizes are equal.
The driver sizes are not equal.
The ep350, ep500 and HSU vtf3 have 12" drivers , the SVS subs have 10" to 13" drivers. The Epik has two 15" drivers which is equivalent to a 21" driver. Furthermore, with the two opposing drivers you get reduced enclosure vibration.
I agree that he will probably be happy with any of them, since they are all good subs. But, to me the Epik seems to be in another league just looking at the specs and price point.
