Ok, so you're over in Australia. I'm not actually sure what $600 AU dollars translates to in American currency But here's the thing:

You can get a brand new laptop http://www.dell.com/au/p/inspiron-11-3162-laptop/pd?ref=PD_Family starting at about $300. You can get a brand new, really good laptop for $550. That means the hardware is modern(vs hardware from a few years ago, you'd be amazed how much can change in just a few years) and a brand new unit is always going to have a better operational lifespan than a refurbished unit.

Think of it this way: the machine id designed with an operational lifespan of about 5 years. Even refurbished, the hardware litterally decays. So if you buy a 2-3 year old refurbished machine, you've only got so much time left on it. It doesn't matter how repairable it is, replacement parts will cost more than you spent on it.

Obviously I'm not telling you how to live your life, but I've bought a loooooot of computers in my life. A lot of new, a lot of used, a lot of refurbs. For the money, new is always better. This is double true for laptops.

It wasn't even power creep; it was Talons, from The Deck of Many Things.

The kobold speed boost is supposed to also work in the cannith challenges.  The loot from those has some gems.  Personally I can't see the speed difference.  I often forget to grab the damn hat when CC opens for 2 days or whatever.  If I bother at all, and there are still a few items from there that I wouldn't mind having.

Dell and 'upgradable' can be two separate things entirely.  Dell likes to use proprietary connectors to force people to buy their spares, especially with power supplies.  If you can find out how many memory slots the mobo has, and how large a memory stick each one can hold, more power to you.  They don't usually publish that information and you might find that you can't even add more memory.

though by 15 you can have a greensteel conc SP item.

Show me a hat that has Archmagi and Concentration +15 on it for a level 15.  Crystal Cove has one.