I think the Tascam 16 channel series of interfaces has always been the best bang for the buck bar none.
I have the older us1641. That was replaced by the us1800 and now the one you have purchased. They have always had a street price of around $300.
I can use all 16 inputs no problem.
I use the 8 XLR inputs for mikes directly
I then use the back panel line inputs fed from line outs of a mixer. You can purchase a mixer that outputs 4 signals for under $100.
I use the instrument inputs from various scources like amplifier line outs or DI boxes.
The one option I have that most don't is I can input to the SPDIF via my Yamaha 01v Mixer.
I can record keyboards ( or digital drum pads) as MIDI.
So now thats 18 channels all with a $300 interface.
Note to all interested :
If I use WDM mode I can use the USB stereo out from my Yamaha MG UX 16 mixer. Which is also possible with most other audio interfaces. My Focusrite 6i6 does not run in WDM mode so you need to check into this first. So if you have an extra say, 4 x2 interface or any other amount, that gives you extra channels. It does not have to be the same brand or model. You can always record audio in WDM mode with out issue. You switch back to ASIO for overdubs and mixing and going crazy with VST's.