I went through the same thing. The 10G cooler will limit you to about 25 pounds of grain, so you won't be able to do high gravity 10G batches. I originally had a 10G round cooler for 5G batches, but went with the 70QT Coleman Xtreme rectangular cooler. I should be able to get around 42 to 43 pounds of grain to max that out. At Walmart (do you have those in Japan?), the Coleman was only $40, so it's pretty much the same price as the rubbermaid.
I didn't use a pump the first time I used the new system, but I just bought one for pumping through my chiller. Basically, I took the cheesy/cheap way and just had 1G rubbermaid pitchers and transferred liquids that way (with a basin/bus pan under both pitchers so I didn't spill anything). However, it failed on chilling...normally, I had enough height on my BK to allow a gravity drain through my CFC, but my new BK isn't as high now.
Personally, I would upgrade the 25' IC. Either go with a CFC or a larger IC. The 25' IC is going to take a while to chill big batches.