The Quadra was not very interesting. I've had a Quadra 840 AV for a very short time. My Amiga 4000 with Blizzard 68040 accelerator was running MacOS 8.1 via Fusion much faster than the Quadra made in the same time. With the Blizard 68060 the Amiga outperformed even the first Powermacs! Back in the 90s I prefered the Powerbooks, because there was not such a thing with AmigaOS. My first Mac was a PB 145b, bought in very good condition in 1996 for 100 DM (about 50 EUR or 70 US $), later I switched to the Duo line, with the "top" Duo 280c. Today they would call it a netbook.
And if you want Unix on a Quadra: Try NetBSD! That would be the best option. There is a port of "PearPC" for NetBSD, you could even start MacOS X on a Quadra! I've heard it takes about 2 weeks to see the start-screen... :-D