Windows 8 drivers are still developing.. download the drivers from the wireless manufacturer not Samsung and try it.
I am not surprised though at differences between wireless.. card using different chipsets and different antennas will give totally different results.
But you can help a bit.. setup the TC with SMB names.. short, no spaces, pure alphanumeric.
Set the name for 5ghz different to 2.4ghz so you can change over.
Set the security to WPA2 Personal which is the only one suitable for N wireless at home without a server.
Set 2.4ghz to manual radio channels and test, channel 1, 6, 11 in turn.
Try up close using 5ghz as it is faster.. but to get full speed you need a broadcom 450mbps card..
Remember wireless chipset like atheros and broadcom never quite see eye to eye.. it is one reason you buy the same brand.
Solution.. buy a cheap edimax wireless router.. plug it into the TC and use it for wap only.. I just did this for a friend.. works much better than TC or airport extreme on a PC. But I have not used win8 yet.. no idea if that is going to be problematic.