I note that your amp would be wired like 1.5ohms per channel... IIIISHHHhh!

Some amp accept that but most commun amp can not..
What is your amp? and the fuse on it?...

usually 2 x 35 warms at 4ohms are fused 15A

Also you may be surprised if you drive it at 3ohms! it could give you less power!
in this case the switching power supply inside can not give the needed current for 1,5ohms stereo (or 3 stereo)but it is built to pull enough current at 2/ch stereo or 4 mono...

To amswer your question, if your amp is ok for 3ohms you can use 2 6 ohms or 3 8ohms speakers..