I need some help finding the right parts for my new lab PC (Patreon)

Hello my patrons! So it turns out that my Lab PC, which has been working flawlessly, needs to be replaced. The Elgato capture card I bought requires a 4x PCIe slot -- and this machine only has two 16x PCIe slots inside. The GPU takes the place of one, and I have a 4x -> Four 1x slot splitter in the other. (Used for mining) 

I have a PCIe IDE card plugged into one, to support the Zip-250 drive and I have a Firewire PCIe card plugged into another, for retro video capture. Then outside the PC, a 3rd PCIe splitter is sitting there where I have a recently purchased Elgato quad capture card. It turns out the Elgato card requires at a minimum a 4x slot to work properly (confirmed by Elgato.) 

So, I need to replace this machine with one with at least 4 slots, preferably 5 slots. The issue is I also have other requirements for it. As you can see, I have both an optical drive (Bluray/CD/DVD burner) and a Zip-250 drive. I use both of these in the production of my videos so I do need to have at least one 5.25" bay and a 3.5" bay for the Zip drive. (Or two 5.25 bays)

Size is also a limitation here -- the height being the main limiting factor -- as you can see, I stuck the measurements of this case there which just fits on the shelf. 17" or 430mm tall is all I can accommodate. Due to space in the basement, I just don't have room for a larger case than this. 

This Dell workstation also has a physical RS232 serial port which I do use -- it's very handy to have a true standards compliance serial port as many times a USB Serial adapter just does not work with really old computers. It's possible a PCIe Serial port card would do the trick but I'm not sure those exist and create standards compliant +12/-12 serial ports.

This Dell machine is very quiet which is important as well, since I use this machine while making videos.

I need help finding a new that can accommodate a new motherboard that has the extra slots I need that fits in the space I have and also has room for the optical and Zip drive. 

One last possibility -- the second PCIe slot in this machine is a 16x slot -- so if a 16x -> four 4x slot splitter exists, that might work. I do have the capture card sitting outside the PC as it's pretty full inside with two extra cards just "jammed" inside. I suppose if an external box existed that went from one 16x slot inside the machine to four 4x slots, that would do the trick too. 

Any help finding the new parts would be greatly appreciated! 

Summary:

- Must fit in the space I have
- Must have the enough PCIe slots to fit everything I need
- Must have two drive bays to handle the Optical and Zip drive