Re: engl Vs mesa Vs marshall
If you like Turbonegro and other rock like that then a rectifier is an awful choice as they suck at medium gain kkkllaaaaaannng. You know...the big open chord glory! Another choice could be a Soldano Avenger as well. I would go with an amp that has high gain but is coming from a Marshall direction so you can dial in rock as well as metal. I played the new Rivera Knuckleheads and they're all big rumble and fizz, no definition or spank. Both them and Mesa come from a Fender direction and has Fender ever had a good high gain amp? I rest my case.
Also it's not as fancy but the Peavey 5150 is a great and inexpensive high gain amp. Handles down tuning well and was also used by Turbonegro as their backline a few tours ago. It can do the rock.
The Zakk OD pedal from MXR is a Boss Super overdrive with a better tailored low end response so to have both would probably be redundant. I just got the Dimebag crybaby and love it but the Tremonti wah is the best one I heard from Morley and also pretty good.
To ask opinions on picks is just plain gay

mg: . Unless you live in the mountains amongst goats go buy a bunch and have at it. I don't think picks bought sight unseen will break the bank!:headbang:
Remember, high price, jack of all trades amps tend to be Masters of none. It may be more rewarding and less expensive to buy individual cheaper/established amps that excell at one particular sound and then use a switcher. eg. JCM800 for rock and 5150 for metal. Or the Zakk OD into a JCM800 gives you a whole range of sounds right there. That way if you tire of one tone you're not selling an entire rig to change it.
I owned both a VHT Ultralead and a Bogner Ecstacy and still found myself going back to one channel Marshall's and supplementing with pedals because for me one glorious sound was worth more than three good ones.
Good Luck....unfortunately there's lot's of good choices but hardly any chances to hear them. Sound clips on the internet are a horrible way to shop for an amplifier.