Next Canoptek Spyder Done

Nick speaking,

Like most Necron players using the old Codex, Tomb Spyders weren't a major part of my army ideals. I had a couple, and I did use them now and again, but of course, things are different now. A few weeks ago I found myself a nice cheap second had Spyder in my local hobby store, which I quickly purchased. It had a half decent paint job i.e. it was dry brushed silver, but it didn't match the rest of my army. Time for a quick strip down, repaint and a bit of extra detail to the base, including a few of my green stuff Scarabs to bring it all together...

So, that gives me three Spyders in total, not bad, but how many Spyders should I aim for? Nine sounds good, and with my green stuff scarabs working out so well, I could easily get together sixty Scarab bases, but is that over the top? What is the ideal amount of Spyders/Scarabs in a 1750/2000 point list?