Diamonds usually fit pretty well into your desired scenario.
Another option (if your diamond fund is depleted or earmarked for future upgrades) is to do what I've seen a lot of folks around here do when they're selling their home. The include their "media room equipment" with the house - usually claiming a "value" of $20,000 to $30,000. You can easily justify your expediture (and sound judgement/fiscal responsibility) by the potential windfall you receive when you sell your home. Your potential buyers will be able to audition your set up - be blown away - and fund your future and upgraded system.
Kudos to your investment skills !!
