Minor point: High Gravity is the name of the store (nice people there, too!)... The system you're looking at is made by - or at least mostly made by - MiniBrew out of California. Googling for MiniBrew should turn up their page, i think it's just minibrew.com
Note that for a thousand bucks, you're getting the whole pump-and-barrel rig, with copper heat-exchanger, quick disco's, all the works. I agree that that's not quite what you're looking for, as you have most of a system and are just looking to upgrade components.
I am fighting the same desire right now, I don't use a HLT, so I have to move lots of buckets of water around. The Keggle is too heavy to lift, too..
---------
I would suggest getting a large-size cooler for both mash-tun and HLT. Look for a 100+qt Coleman or other. Something like this:
a 150qt model holds over 37 gallons... that translates to 90 lbs grain at 1.25 qt/lb. Which means that your 15 gal batch could have the equivalent of 30 lbs of grain for each 5 gallons. That's on par with about 1.150 gravity. A 100qt model might fit your needs too.
Then do a simple bulkhead + copper manifold for the MLT. Bulkhead, valve, and o-rings can be had for about 10-15 bucks, and then the cost of the copper for the manifold will vary with design and local prices. These of course are assuming in-US prices. You didn't mention much about your situation (coming back stateside? looking for shipped? etc)
For the HLT, it's a little more difficult... I would cut two holes in the side of the 2nd cooler (less than 100qt for this one?) and mount two 120v heater elements. I've not done my electric HLT yet but there's a lot out there already in terms of how to attach and control the elements. If you could find an "Ice Cube" cooler, they might be preferable since they are taller, and not the typical shallow rectangle cooler. You could do a single 240v element in an Ice Cube cooler much more easily. Would require a 240v element though.
-------
http://www.brewmation.com/HLT.html sells a VERY attractive unit for a good price. I really kind of want to buy this one, myself, as it includes a Love temp controller. Very nicely made.
-------
Probably overkill, but
http://www.dmebrewing.ca/cat_equiplist.asp?cattype=1 <- this place sells pro-level brewing equipment, they have tanks in the 5-10bbl range though. You wouldn't have to go straight to a 30bbl system. Again. I know it's more than you need. But it could be a handy source to talk to, who knows.
-------
Finally, if you go back to the High Gravity Brew page, and instead of choosing the HLT/MLT system, pick the boil kettle. Select the following options:
Build Your Own Brew Kettle (BYOBK)
Vessel Modification: Drill Hole for 1/2 in. Ball-Valve$20.00
Brewpot Hardware: BrewMometer 3" Dia. Weldless Thermometer $33.00
Vessel Modification: Drill hole for Brewmometer Weldless type $20.00
Brewpots: Stockpot - 82 Qt. Stainless Steel $174.95
Vessel Modification: Drill Hole for 1 in. Heating Element $25.00
Brewpot Hardware: Weld-B-Gone Deluxe + $59.95
Brewpot Hardware: Heating Element - 5500W Installed w/ Weldless kit $74.95
Product Subtotal: $407.85
Voila, 82qt Hot Liquor Tank with valves and element pre-installed for under $500. Then just buy a cooler and do manifold+valve for your MLT. There's really no sense in buying a pre-made MLT when it can be assembled in 30 minutes with components from any plumbing supply store.
G'luck with your search!