Since you are talented and confident, then diving into the powerbook will be easy; here is an additional guide:
Daystar seems to be the card of choice and it is a 433MHz G4. The 33MHz is not worth the money but the G4 is of benefit if you are running applications that take advantage of the G4's AltiVec and these are mostly video processing apps. This G4 CPU will not improve the loading speed of DVDs nor increase the display rendering speed of downloaded webpages
The Lombard is also VRAM (video RAM) constrained at 8MB with no way to increase it.
I really don't believe the upgrade itself will be of much benefit for your purposes. In the past one companny offered a 900MHz G3 but I believe it had heat and/or other issues. I can see the benefit of an upgrade card under this scenario: You are wed to the Lombard and want to run Tiger and also have 512MB of RAM available (the upgraded CPU will solve the memory issue). If you wish, head over to this site...
...and select just the Lombard powerbook while leaving the manufacturer blank. There are approximately 60 reviews of various cards.
If I may humbly make this observation...you are working with hardware that has speed traps...8MB of VRAM, 66MHz system bus, 400MHz CPU...and all that you would like to upgrade will have little benefit in overall performance. One could argue that the performance you have in 9.x will be faster than a move to 10.x. You also have to be careful about putting money into older hardware, especially an approximately 7 year powerbook.
I would urge you to try this first: Remove the top 256MB memory module, then install Tiger on your 8GB HD. I have installed Tiger using as little as 2-3GB of HD space. If your current HD is highly fragmented (and it probably is if you have never used a utility like Norton Speed Disk or have never erased/installed the OS), I would erase it, install 9.x + XPostFacto, then Tiger. This will give you a real-world feel as to how Tiger will perform when loading web pages, DVDs, etc, without any additional expenses.