For a Pentax DSLR you'll want to keep the trigger voltage very low. From memory I think my flash is about 5 volts, used on a K7. I would think the K-x would be around the same requirement. If the flashes you have are 20 or 30 volts or more, you could fry your camera if you put any of them on the hotshoe. As Ash has said, remote triggering is the way to go. I have a little gadget - don't know what it's called, because it was given to me by someone who didn't know what it was. It's a small, cube-shaped gadget with a lens in one side and a hotshoe fitting on another side. It clips underneath a flash and you can either attach that to a remote arm which screws into the tripod thread of your camera or stick it on some kind of home-made stand, old tripod, whatever.
As you can tell, I don't know a lot about using flash, but I've found this gadget to be perfectly safe, triggered by either the on-camera flash or my other, (5 volt) flash mounted on the hotshoe. Someone will know what the gadget is called and you can probably pick one up for a few dollars on Ebay or from a camera shop.
If you decide to test the trigger voltages as knaff rightly suggested, make sure you use a digital multimeter. Analog meters can give some seriously wrong reading. There's directions on how to do it on the Forum somewhere. Just do a search and you'll find it.
PS. I've just re-read Ash's response and I think the gadget I have might be what he refers to as an optical sensor. Mine seems to work OK. I guess if you just want to play around to see if flash photography presses your buttons, it's a cheap option.
Last edited by Wombat; 02-24-2011 at 09:08 PM.
Reason: Addition