Indyws6,
I started the same way. LANs and WANs back in the day before high speed switches came along and we were on 100BaseT hubs segmented by routers. I built all the networks and setup and maintained all the Novell, NT and UNIX servers. I loved the work but the hours were hell. I went into application development and consulting for many years. The money was good but keeping up with technology sucks. Always a new version coming up and having to learn the latest technology. Over many years I worked my way out and now I only do Enterprise Architecture work. I don't get paid for what I do but rather what I know. It's a great gig.
I'll be honest with you. You might have enjoyed the network stuff, but it's a deadend for most people unless you get all your security certifications and get into doing independent security audits. If you can pull off what you are doing now, you could end up with a nice little gig in the end. The valuable person is the one that knows a system from end to end and not a particular piece. What you are dealing with now is what they pay me the big bucks to make sure doesn't happen in the first place. You have a tough job ahead of you. I'll give you a few pieces of advice. It looks like you have identified all the players and what needs to be done. Do you have the authority to use resources to do the work? If not, you are going to have to work it up your side and have it fall back down on theirs. If the powers that be are not committed, it's not going to get done. If you have that taken care of, just make sure the time tables are doable. You were brought back for a reason and whether you like it or not, all eyes are on you. You've got to make the situation realistic. Last, document everything. BCC yourself on every email you send out and CYA as no one ever seems to remember being told to do something.
Also, be very careful throwing hardware at a problem. Especially with the data problems you are having. I would make sure your DBA's know what in the hell they are doing. Is it a custom database? Is it normalized at the right level? Most important, have they ran explain plans on all the SQL. 90% of the time I deal with database performance, it's an index problem and SQL statements are doing full tablescans. If you don't have a DBA running explain plans on every SQL statement in a application to ensure indexes are being used correctly, your developers will kill you as very few of them know anything about tuning SQL.
Status reports do wonders for motivation. You don't have to use names, but if you summarize the areas involved, schedules and throw a few red statuses on an area, it will get their attention.
You may know all of this already so don't take me giving you advice the wrong way. I been in your situation and the key is to manage expectations, surround yourself with good people to get the job done and stay on top of everything. Nothing like a CTO telling you he needs something done in 6 weeks with $500,000 and you tell him it's going to take 6 months and triple the budget if he want's it done right. If you have the reputation, they may not like it, but they usually won't question you.
Good luck and if you have any questions or just want to run something by me, feel free to PM me.