There is a manual on the web
http://www.peavey.com/media/pdf/manuals/80301434.pdfI'm making some assumptions but yes you can probably use an 8-ohm (or higher) speaker with no problem.
The label indicating speaker jacks are paralleled means that when you plug in multiple speakers, the speakers are attached to the amplifier in parallel so if you plug in a single 8-ohm speaker, it sees an 8-ohm load, if you plug in two 8-ohm speakers, it sees a 4-ohm load. You plug in two 4-ohm speakers, it sees a 2-ohm load. Since the minimum load is two ohms, you would not want to plug in a pair of 2-ohm speakers as that would risk damage to the amp. Three 4 ohm speakers would also be bad. The latter two examples would present a load of less than 2 ohm.
Edit: Also, I would recommend against mixing speakers of different rated loads or efficiencies since you will not get even sound from both.