I have not set up SSD drives for myself, but have worked some with other computers, so others with more experience should chime in for more info. Basically I have found them to be not really different in terms of set-up of partitions and the rest using Disk Utility. Again I do not have alot of experience with it, so take it with a grain of salt. In terms of size of drive, usually I would go for the largest possible. I would think 256 Gigs though is probably the minimum based on what you think you will want on the machine and cost. I have an Air in the house (11") with 128GBs and it does the job, but there is not alot of software on it. But with what you do, I would guess you would want more real estate.
You mentioned you want to use Snow Leopard still because of Quicken, and not sure if you are looking at a new laptop or just upgrading your existing ones. The new laptops may (with the release of Lion) stop you from putting Snow Leopard on them. Apple has done that before, though with the machines in the pipeline the current machines, you should be probably be able to install SL on them still.
Alternative personal money management programs you like for Mac?
I have tried various programs such listed here Financial Apps
and
iBank
Liquid Ledger (Updated for Lion)
There are some pros and cons. It was a year or two ago and I think there were some issues with tracking costs basis of stocks and/or updating prices which I found a bit awkward to use, and like every software some pros and cons. Many offer free trials, so you may want to check a couple of them out and see which ones do what you need and how difficult it would be to transfer the information over to the new software. Liquid Ledger and iBank I think were the ones I liked the best. I ran into the issue that I was converting from Quicken that I had on an old Windows machine, so that may have made it more of a pain since Quicken (PC) TO Quicken (Mac) was not an easy or complete process and probably where the basis issue came in.
Not sure if you looked at the FAQS Quicken, but they list what the plans are for Lion. I would not hold my breath on waiting for an upgrade for Quicken, but who knows. If they are writing for the iPhone and iPad, seems strange they have not also updated the other products. Maybe they were waiting for Lion?
What about waiting for Thunderbolt drives, will they be a better option to SSD's?
Thunderbolt is the I/O while SSD is the drive itself. So not sure if you are comparing apples to apples here? (I am still drinking the morning coffee, so maybe missed something.)