Looking at your requirements, as you don't use your computer for gaming, you're toying with the idea of an ipad and finally the scripting thing. I reckon your best bet would be a macbook air. The observations about the lack of flash on an iPad is relevant if moshi monsters is the order of the day, although theres a moshi monsters app for the ipad, it's not the same as logging in properly. Although, iPlayer, 4od, ITV and Channel5 all have iPad apps, so watching TV, is fine on an iPad. Not only that, but there is also the Catchup TV app, which allows you to watch live Tv on the iPad. I've been a PC user for 15 years and a mac user for 4 just over years. My old Mac (judging by ebay) is still worth about £400 and is still as quick as the day I bought it... and no anti virus on it! Just treated myself to my second mac (an air) and I'm staggered at how much quicker it is with a SSD (even with only 4GB of ram). If you keep your eyes on hot uk deals you can occasionally pick up a 64gb one for £500 to £600 which, as far as I'm concerned is an absolute steal. I've just acquired one of the most recent ones with 4gb of ram and it edits video like you wouldn't believe. I'd strongly urge you to go and have a play with one in your local PC World. They're so light!
I'm guessing that you're a quality HiFi buff, so you'll have an appreciation of how well made, well designed tech can make your life easier. No one I know of, that has bought a Macbook since I bought mine, has ever gone back to a PC. Although our IT tech at work uses both platforms happily and is perfectly happy with Windows 7. We had one for a while, but the following may explain my loyalty.
We also have a Time capsule with an attached HDD, which I store films and music on, although my library is kept on my Mac, we can stream music from the Mac, to the living room via our Apple TV, and into the room upstairs via an attached Airport express unit. Both of which cost us less than £100, yet we have the same flexibility as a Sonos system, or something far more expensive. And the LAST thing, is if you own an iPhone, you can use it as a remote, and send the music to whichever room you want. If the Mac's aren't on, there's an App available (without jailbreaking) called filebrowser (for iPhone or iPad) which detects the attached network drive and allows streaming to the device, or again, attached airplay devices.
Hope I haven't bored you, I know there are advantages to cost and gaming flexibilities from PC's. But I'd strongly urge you to *** into a PC world or an Apple store if you can and have a play. Best place for bargains as well is the Apple Refurb store (scroll to bottom left on Apple Store website). Thats where I got mine from.