Here are most of your options
1. Get the ErgoDox- $250 w/keycaps It has everything you want. You will have to assemble it or hire someone to and it may lose some proficiency on a std. keyboard but probably is your best choice.
2. Freestyle or Goldtouch- $100 No programability, membrane switches, staggered layout, no thumb cluster but two halves are tent-able, the Freestyle is separable to 20"and both can be skewed.
3. Truly Ergonomic- $250 Good build, some splitting, matrix layout. But no tenting some minor firmware issues and the worst communications to customers I have ever seen.
4. Kinesis Advantage- $280 Many people here love these. Programable, one piece split, matrix, thumb clusters and contoured. I've never used one but I would consider it.
5. Maltron- Similar to Advantage but more expensive. I don't think they are programable but have other features.
6. Microsoft ergo 4000- $40 Split one piece design, slight tent, better hand positioning than conventional board.
None of these are bad choices depending on your needs and budget.
Other thoughts-
While the staggered layout is a vestigial remnant from mechanical typewriters, I think the matrix is an improvement but not essential.
Ergonomic solutions fall into general categories but one size doesn't fit all. Although it is usually impractical, it's best to try out before you buy. Unless of course, you want to have a closet full of keyboards like the rest of us.