If you want to run with an arcade monitor, you will have to use an add-on Graphics card like an ATI Radeon 7000 or better or an ArcadeVGA from Ultimarc (which is a modded Radeon).
Also, you will need a slot to put it in. If you say the SX-280 has no slot for a graphics card then that will not work. If the other one has a half-height slot you can use it, but it is difficult to find a half-height graphics card that will be suitable for your application. It is not impossible, but it may be a hassle.
I have used similar PCs for MAME cabs using a normal PC monitor and they work great. But if you really want to do an arcade monitor, get a PC mid or full-tower with an AGP or PCI-e slot. They are easy to find used for about the same price. Look on Ebay and see if you can find a PC refurb warehouse. They will have tons of off-lease PCs for good price.