I look for balance. I learned long ago that it's cheaper and more efficient to buy a smaller, light laptop or tablet for portable computing and a good tower for my home computing needs.
It really all depends on how you use your computers.
If you want/need a computer on the go, but don't need to play games or do video editing on it, get a simple laptop for use during travel. You can usually find something around $200 at BestBuy or online. In this way you can use the money you saved on the laptop and buy a good desktop for all your heavy CPU needs.
I went this route a couple years ago and spent a total of $1500 dollars. It may seem like a lot, but not when you take into account that I now have three laptops (ranging from a light but stable mini-notebook to an entertainment Sony Vaio) and two desktops with a multiple monitor setup.
Everyone thinks you just need a great laptop, but with the advent of cloud storage and computer networking becoming so simple now, there's no reason not to have different computers for different tasks. The best part is that towers last twice as long as laptops, and are cheaper to upgrade. I still have a tower I bought almost 8 years ago, and it runs faster than my friend's brand-new vaio. Just keep it clean and up-to-date and you'll be fine :)