I think you'd be best seeing how far you can get with your current laptops before upgrading. On the software front Reaper would be an excellent choice on Windows, very cheap and CPU efficient.
Cheap audio interfaces have come a very long way, I'd look at what's being sold second hand in your area. Something with a Hi-Z input if you're wanting to record your guitars directly though the interface.
Cheap audio interfaces have come a very long way, I'd look at what's being sold second hand in your area. Something with a Hi-Z input if you're wanting to record your guitars directly though the interface.