I'm using mogul socket 315W CMH lights. Otherwise their the same, but they fit my bare socket vertical cordsets this way.
I'd say that 315W CMH lights can be subbed for about 500W of HPS.
DON'T PAY $400 FOR ONE! Look online, they need not be so expensive.
He asked about veg, and I'm not a fan of HPS (spectrum) or MH lamps (inefficient). Just use CDM/CMH/LEC, they're all the same thing. Be certain that whatever driver you get is both low frequency and square wave to maximize their performance.
If you want a better light, use COB LED.