I've got procyons that I combine with 20K of T5. Works beautifully. But oldmac is right, one Procyon will not replace a 400w HPS, it may possibly replace a 250w HPS.

As much as I like my Procyons, I know they are not perfect with the flowering bands, meaning I try to add some kind of supplimental light in those missing areas.

I sometimes run the early part of bloom under LEDs only, to control temps. This was due to a thread where Stinky (I think) discussed stretch during flower and what part temperature and color have on that stretch. I add T5s later in bloom when temp. is not as critical.

I haven't tried the UFO knockoffs, but would not hesitate to try one. I personally would look for the latest generation tri-band with orange added. But, I haven't done my homework on LEDs lately.