hey,
well, the Spider did have all kinds of tones available, that's one of the big advantages - you could go from sparkling clean to full on gain at the press of the (included) footswitch.
I remember the cleans being very clean and really nice to play on. I quite liked the superheated Plexi sound on it too, particularly if you run a boost into it, it was quite nice. However, without the boost I found the higher-gain settings sounded a bit fuzzy and not brilliant. However, two things to remember:
1) it's a cheap amp, with lots of versatility - its never going to be perfect, and
2) I'm not a metal player and never owned a high gain amp, so I don't know at all how it compares to that kind of sound, it's not a sound I use much.
As for the effects, no I didn't like them much at all. They were useful in a way, but the way they were implemented was kinda useless - it was one dial for all phase/chorus/flange fx, so the 1st 3rd of the dial was chorus (or something) and then beyond that point it became a phaser, and so on. It was a little bit too fiddley for me. Plus, on the included footswitch there is no way to turn the effect on or off unless it's saved to be automatically present within that particular preset. Although, I think they make more expansive footswitches that do have footswitches for the various effects, but you have to buy these seperately.
The best advice I can offer is to try one in person. I know that's a bit of a cop-out answer, and I apologise, but if you're looking for an opinion on what makes a good 'low end chugging' then I'm not really a man who would know! :) I just remember liking the cleans, the versatility and the crunch setting was OK (although doesn't compare at all to the JCM800 crunch I bought after selling the Line 6). It is however, quite compact for 150W and pretty cheap. But as I say, try before you buy; it does so many things, some you may like and some you may not - if you try it, you'll be able to make sure that it does the things you want it to do, well!