preamp matching to poweramp

What does one need to take into consideration when matching an amp and preamp? The models I am currently looking at are the Opera Consonance M500S Signature 300B Monoblocks running at 18w and the Decware taboo running at 6w. I may have found a preamp for the Opera

but the decware is a bit of a question for me.

I gather you should try to keep with in the brand, but I need more inputs than decware preamp offers and I dont have money for 2 preamps.

Check the output impedance of the preamp (sometimes hard to find) and the input impedance of the amp. The ratio of the input impedance over the output impedance should be 10x or greater for there to be no bass attenuation. This is a rule of thumb so take it with a grain of salt. 8x will probably be ok as well. In most cases, there is no problem but with something as esoteric as the Decware, it would be best to check.

Otherwise, I don't think there would be any matching issues beyond personal taste.
You also would not want to pair an amp with a particularly sensitive input stage with a preamp that is very high gain -- you will have very little range on the volume control (9 O'Clock can be full-blast with bad mismatches). This happens, so beware.
Both responses above are excellent, and I can't think of any other important issues other than balanced vs RCA.
Far more components use RCA than balanced, and many that DO offer balanced are not true balanced operation, but only op-amp powered at the output. (So stick with RCA in and out, unless you really have the extra cash to get true balanced units))
Some solid state amps are reputed to be sensitive to DC leakage from tube pre-amps. Some old pre's offered power outlets. While I don't suggest you use them (especially with an amp), they might have compatibility issues there. On the same track and this may sound silly, but you asked so; you might want to have both pieces work off of the same proper native power voltage or it might get a little tricky.
Thanks mcuah for the help. Ill keep this stuff in Mind.