For the utility you claim to require, would you notice a significant difference? No... Not really.
From what you've stated, you don't strike me as a gamer... Neither do you cast the shadow of a photographer, designer, web developer or video editor.
You're burning music CDs, web surfing and doing a bit of word processing. For these items alone, there might be a microseconds difference in processing time, but that's a microsecond no human brain could record in real life terms.
We're consumers by nature and whether it's peer pressure, clever online/televised marketing, or indeed, all of the above, you start to feel like you've got to update in this day and age, whether it's necessary or not.
Frankly... If you're software hasn't been made redundant and if you can still operate within the bounds of your own requirements on a functional level, within an acceptable time frame, I wouldn't bother upgrading.
An extra 1.5 hours battery life and bluetooth is handy, but is it essential to you? Ask yourself that and you'll have the answer best suited to you.
Is this new Sony computer better? Of course it is... A lot better. It's chipset is newer and there's a lot more data being thrown around and you've got a larger screen... But what do you need it for? Unless you want to pursue other creative endeavours or recreational hobbies, I'd put your money into something nicer, like a holiday or a nice meal for someone special.
Hope this helps and please don't think I'm being condescending. I just know what its like to blow money on unnecessary upgrades, but in my case... I've wasted tens of thousands.