I'm in Texas, but have done some business with a company called Augustus Technology in CA.
www.augustustech.com
Never knew they existed until I heard about them on Anandtech forums.
They have many Retail Boxed Celerons - 566, 600, 633, etc. for under $60.00. About $10.00 shipping. They shipped my order within 24 hours via UPS ground.
I don't overclock with the earlier zeal and passion I once had much anymore. Normally I'll try to push 66 MHz to 100 MHz, or 100 MHz to 133 MHz. So, regarding a fan/heatsink, I'd say go with a stock Sanyo-Denki heatsink/fan, which is included with a retail boxed CPU, or you can pick them up for between $7-10. I ran a 300A@450 MHz with an earlier, smaller Sanyo-Denki heatsink/fan for months at a time. It should be sufficient. Maybe get a decent case fan too.
But again, do invest in a quality slotket. Name brand. Not some generic stuff.
The proverbial "sweet spot" (likely overclockable) Celerons seems to be in the 533A - 633 range. I believe the 566 holds the greatest potential, but be sure to check over at the CPU/Overclocking forum first. I'm an old school tech anyway, so don't hold my recommendation on that as gospel.
Regarding the voltage: 1.65v is what most FC-PGA Celerons are set. Some early Celeron IIs are at 1.5v.
The Max: I had a 533A to 800 MHz. 8x100 MHz FSB. Tried taking it to 112 MHz FSB. Wouldn't do it. Increased the voltage to 1.6v and I fried it. Again, check over at the CPU/OC forum. There are some experts over there. Lot's of people on Anandtech forums take 566s to 850 MHz. And higher.
Your board should also run a Celeron 800 MHz (100 MHz FSB) with no problem.
I love BH6s. Was going to sell one of mine, but couldn't bring myself to do it.