Well, after upgrading to 7.4.2 firmware of my 1T Time Capsule and realized it sucks (our Windows XP machine gets dropped connections all the time, the MacBook stays up a bit better but very frequent drops there too), I was looking for the old 7.3.2 firmware, but Apple in their infinite wisdom has removed the possibility to download this firmware form their 7.3.2 download page, I finally found this link:
http://apsu.apple.com/data/106/061-4874.20080627.8U65r/7.3.2.basebinary
on this:
http://discussions.apple.com/thread.jspa?messageID=8396597
page, and concluded that it works for the Time Capsule also even though it is mainly the AirPort Extreme 802.11n Base Station that is discussed on the page.
If they end up removing that one to, feel free to contact me (by leaving a comment here) to get hold of the 7.3.2.basebinary.