floatyurboat, I buy a Pelaj Nemesis spearguns and change handle and head by Speardiver. The Speardiver handle is the best I use, I have 7 spearguns. I do not think Rob Allen speaguns is any better than Speardiver Phantom.
Buy spare shaft, I recommend Rob Allen.
I always consult Dan on fishing equipment, he is very knowledgeable about the business. He does not sell garbage in his store.
A speargun 100 is fun in corals caves but ... great reef fish and pelagics you will need more ... Do not use < 110.