If the speakers are wired in parallel the impedance lowers:
Za= impedance of speaker 1, Zb of speaker 2.
Zt = (Za x Zb) / (Za + Zb)
Zt = (8 x

/ (8 +

Zt = 64 / 16
Zt = 4 ohms
Which is great, as your amp handle that.
If the speakers are wired in series the impedance raises:
Zt = Za + Zb
Zt = 8 + 8
Zt = 16 ohms
Too large an impedance at the amplifier is no way near as big a problem as too low - it will normally just result in a weaker and quieter output so...
Give it a whirl with 2 cabs - if it's louder, all good. If it's quieter look at how the links are wired....