Q: using  20" cineman display with a 9600/300

I don't think you will be able to jump directly from BD-15 to DVI.. I would try to go DB-15 > VGA - VGA > DVI. Or maybe you might find DB-15 > ADC - ADC > DVI.

Daisy chaining the adapters can work, I have contented a DVI monitor to a thunderbolt iMac with I think VGA in the middle when I was waiting for a new monitor and used a spare I had.

...or you might find a PCI based video card that will output DVI? Radeon 7000/9000 card?

you can go DVI to VGA with a converter.

but to go VGA to DVI in requires more than a pin converter.

you are sending an analog signal to a digital monitor. a digital signal can be interpreted by an analog monitor but it gets more complicated when you send analog to digital receiver.

there were some products on the market for this, I don't know where you would find them. Some monitors still come with VGA and DVI inputs for legacy products because the converters are DVI TO VGA not the other way around. You need an adapter to do this:

http://www.monoprice.com/product?p_id=8214

would not be a male VGA to female dvi (female db15 in 9600 > with a male db15 to female vga)?

http://www.cables2u.co.uk/dvii-female-male-adaptor-dsub15-pi-318.html

If your Apple 20" Cinema Displays are the model shown here at everymac.com, their cable has an ADC connector, not a DVI.  The ADC cable was multi-functional in that it supplied power to the display, carried the video signals, and 5-volts for the (2) USB ports.  Because the ADC cable conveys power to the display, if using one of these Cinema displays when not connected to an ADC-ported graphics card, you'll need to buy the (now-discontinued) external Apple power adapter block.  They used to sell for about $100 at ebay, but the market value may have dropped now.  The graphics cards having ADC ports aren't a PCI card, and that's the only upgrade option for the motherboards found in the 8600/200 and 9600/300.

Additionally, the made-for-Apple (ims/ixMicro) TwinTurbo 128 with 8 MBs of VRAM will likely not support the display's 1680 x 1050 native resolution, since the card's programming pre-dates widescreen displays.  Also, the specs for the Cinema Display indicate OS 9.2.2 minimally.  For a graphics card with an onboard DVI port, you might consider a Radeon 7000 for Macs (a PC version needs to have its EEPROM chip re-programmed to function in a Mac).  The Radeon 9200 for Macs is another option, but requires OS 9.2.2.  The 8600/9600s don't natively support OS 9.2.2, so you'd need the (free) downloadable utility called "OS9 Helper" (if still available), to install OS 9 and then the sequential updates to get it up to 9.2.2.  Earlier pre-OS X versions of the Mac OS don't support the graphics drivers needed to enable 2D acceleration in these cards.