your welcome.. but let me see if I can give you some suggestions first.. :P
Im giving MHO as it comes to mind.. off your list..
1. If your running a old ventrui style you might think about moving up to a needlewheel.. If your running a big airstone style skimmer they have new air pumps and stones I would suggest upgrading to rather then replacing the skimmer (I think there is new promise with this type of skimming that isnt being adopted widely yet).
If your running a skimmer thats rated for a tank less then near twice the size of yours then I could think of two options..
an outright upgrade or.. If your skimmer's outflow can be plumbed getting another skimmer that can be plumed to the intake could be used in series to save you some bucks on the upgrade and give near same performance as a larger skimmer..
2. skimmer pump makes me think of ventrui or needlewheel.. the need for a bigger pump on the skimmer would be a matter of design.. if your current skimmer does not have enough internal volume for the larger pump then it will likely force it to skim too wet for most peoples likeing..
3. your likey using a Mag pump for this job and unless your intrested in going with a deal on ebay on a good used external (Ikwais ?sp? go for great prices yet need sterilized) your not likely going to do much better with a new purchase without a pretty hefty investment (at least in my book)
4. seems the OM squirt would be the best idea Ive seen for water movement thats reasonable.. http://www.oceansmotions.com/
the price of the OM squirt is $125.00 not exactly cheap but users say it holds up like a little tank.. I like that quality in equipment.. :P
this would go with a closed loop of course.. and I favor that over in tank pumps..
5. Unless I had some chemical warfare going on in my tank I would tend to say that chemical filtration for me would be out.. I wouldnt use it unless there was a bad emergancy then I would likely tie in one of my old canister filters into the main line (closed loop or return from sump) and fill it up.. you can also use it more passivly in the sump in bags so you kinda have a chemical media chamber :P..
as far as doesing goes that would depend on what you want to dose.. if you have a fair amount of SPS
then kalawaster/pickeling lime or what have you, depending on uptake vs. your pwc
's, might be on your list, Im pretty sure melv's has a DIY
for that.. but if your wanting to dose something else???? Im not sure I would dig too much of that going on either.. that would depend on how often and how much you change your water (how closed is your system I guess would be a good question)
I keep hearing dont add what you cant test for.. check out this link.. lol
so.. anything on that list is game.. to dose? (assuming its needed ellement)
these are just some of my ideas.. if you would like some coments on any of them just ask (I have this thread flaged, I dont do that, I wanted to help the rev man out!! :P )