Normally I'd post here about my '99 4003, but this time I need your valuable suggestions on something else.. Sorry in advance if it will sound a bit out of the context

We want to set up something like a home studio, that we will be able to record a bass guitar and a drum set, and receieve all the output while we are playing through headphones.
In the drawing attached you will see what we are trying to achive. For now we have an electronic drum set, a rick 4003, a bass amp and a PC. I guess we will need an external sound card (or something to do its' job) a headphone preamp(we don't want to be noisy), a preamp or a processor ( I am a huge Chris Squire fan, I want to replicate his sound as much as I can. I have rotosound swing bass 66, but I don't know how it is going to sound through headphones.) and a software to control, record and receive the sound without any delay.
I'd very glad to hear your advices on this, considering that we want to maximize the quality of the sound with limited amount of money. Plus I have no experience about these stuff, please feel free to correct any mistake I did in the flow of the drawing and in the question.
And sorry If I shouldn't have posted it here

Thanks!