Simple Driver Question

Dear all,

if I select a Buck driver -is it's output voltage the same is the input voltage, and it's just the current that is regulated? Some specify an output voltage, some do not. I am assuming if they do not they scale themselves to match the current?

I am a bit confused.

What I need is to drive 2* Bridgelux ES LED arrays of about 800lm each, and then mount them in the molex mount/cable clamp and finally fit a 50degree reflector.

links for the parts I am considering:
http://uk.farnell.com/bridgelux/bxra-w0802-00000/array-warm-white-800lm/dp/1787315
http://uk.farnell.com/molex/180150-0000/led-holder-bridgelux-es-w-o-lens/dp/1860614
http://uk.farnell.com/ledil/c11508-brooke-w/led-reflector-led-bxra-c0800-1200/dp/2095794

I am really struggling with the drivers. I shall be using mains power, so I don't want wakky voltage requirements, I'd like to use an off the shelf power supply, 12/19/24v etc.

If anyone can easily match me up an LED and Driver from those pages, that would be lovely. Or just explain how to match them.

Thanks for your time

Aaaaha - I didn't see that I can buy them potted!
OK, this should save me some soldering.
http://uk.farnell.com/xp-power/ldu2030s700/led-driver-dc-dc-constant-i-20w/dp/2082740
and
http://uk.farnell.com/bridgelux/bxra-30e0800-b-00/es-rect-800-lm-warm-wht-array-2700k/dp/2070582
driven from a 19.5v power supply should do it, right?
I'll need 2xdrivers, 2xleds and one dual track potentiometer to synchronise the dimming for two LEDs?

so I would have 0-700ma at up to 19v?

That would be much simpler

not checked all the info You gave, but

buck driver --> output voltage is lower than input voltage
boost driver --> output voltage is higher than input voltage