I played around on one and have read ton of reviews and while there is plenty of gain to be had, it borders more on a hard rock voicing and I know I will want an added boost to really achieve the tone I am looking for. Should I be looking for a simple overdrive/boost pedal to use when I need that added "oomph" or go with a metal/distortion pedal straight away?
A few examples of the tones I am looking for: Tool, Alice in Chains, Deftones. Like I said, I have sort of fallen into this heavy metal thing and while it is new for me, I have to say it is fun and very exciting! What are you guys using to push your amps?
There's no one-size-fits-all answer to this - you'll have to find out by yourself what works best for you, since the result really depends on the exact guitar / pedal / amp combo
and how you set them. To summarize (and overly simplify), there are two main solutions:
1/ full-blown distortion pedal on a clean amp
2/ "dirt-boost" on a dirty amp
The first one is usually the simplest to get right - you just have to find a distortion pedal with the right voicing - but it can easily sound a bit "synthetic", at least with solid-state pedals. A true tube-based pedal can give better results, but beware, most of the so-called "tube" pedals are snake-oil (not that they are necessarily bad, but the tube is too often only used to warm the sound a bit while the distortion still comes from silicon - and sometimes the tube is not even on the signal path :-/). Also the good tube-based pedals are far from cheap.
The second solution is way more touchy. Basically, it's about using an OD on low/mid gain settings and full volume to push the already overdriven preamp a bit farther. Part of the trick is to correctly adjust the settings on both the pedal and amp. The other part of the trick is to find the pedal(s) that will work fine with your amp (and guitar of course), and given the tweaking required to make both work together it can be a rather involved process. Also, it doesn't work with all amps - my experience is that the more gain available on the amp, the less it takes dirt-boost fine. IOW, this usually works better with more vintagey amps than with modern hi-gain ones (OTHO, those amps are supposed to have enough gain on tap that you don't need to push them further...).
There are of course "intermediate" solutions that are still based on stacking low/mid gain stages, usually on a "about-to-breakup-but-still-clean" amp (ie David Gilmour's booster => fuzz => pushed Hiwatt amp or SRV's tube-screamer => tube-screamer => pushed Fender amp), but it's still more or less about stacking gain stages, and getting the respective gain / clipping level right.
My current amp is a custom made thingie with a blackface clean channel (one gain stage), an "orangeish" crunch channel (two gain stages so think of a fat bluesy crunch), and a SLO-inspired hi-gain channel (four gain stages - the SLO has five). The clean and crunch channel are very pedal-friendly and work fine with about any of the OD / distortion / fuzz I tried, I mostly use a Xotic EP Booster and a home-made TS-808-based OD here. The SLO channel doesn't require anything more IMHO, but from what I tried only the Dano CTO-1 (which dave_mc mentioned) works with it - and it has to be set on low gain and not too much above unity volume. Anything else is just OTT and ruins the tone. FWIW, the CTO is also the only dirt-box I found to work with our singer's Peavey Classic 30 gain channel (while the clean channel takes anything ok).
To make a long story short: the best modern hi-gain I've had so far were with either a hi-gain tube pedal on a clean amp or a true hi-gain amp - and the best old-school hard-rock tones with a stack of either two OD or a treble boost + OD on a cranked vintagey amp.
