Yeah Avalon's DI is great, but it has inherent EQ curves soooo.
The Radial ones are good as well, but most (maybe all) Radials will only get you to mic level, not line. You need a clean with gain box. I know there are a few DI's out there that do the jump from instr level to line in one hop with tons of headroom and no EQ. With a Stingray you gots plenty of EQ anyway! I use mine constantly!
Power amps, there are tons out there. I myself would want tube power. Good tube power is very clean. But solid state is light, cheap and decent. QSC, Crown and Crest are good. Behringer, Peavey, Soundtech, etc are not so great.
Also ifyou really want to get tehfull tone of your bass its all about headroom and preserving those transient details. I have heard very few mainstream bass heads that do that. Including many of the ones already mentioned. Theyall round off the edges of the transients assuming you want that "warmer" sound. That is likely a lot of what you hear in headphones that does not translate to amps.