If I was buying right now I'd go for a 1200 with the fastest (preferably PPC) accel I could find, preferably towered with the Z4 zorro/PCI board. This lets you use el-cheapo PCI PC GFX cards, sound cards, modems and network cards. Unless you want OldSchoolGaming ONLY in which case, a std A1200 will be fine.
If I was looking to the future then it's got to be the AmigaOne G4. Because it's socketed you can plug in a faster chip (if you want/as it becomes available). You can use AGP GFX cards, USB devices, ATA drives etc., but the best thing is that despite WinTel machines having higher clock speeds, the G4 is a very efficient CPU and OS4 is a very efficient OS with low overhead, which means that the subjective speed of the machine (how fast it feels to you) is a lot higher with the A1 than it is with the PC - even with 2GHz+ CPU!
If you have a 1200, see how it feels when you open a window. Now try the same thing on a PC running W98. Spot the difference! Unless you're using 600MHz+ the A1200 feels to do it faster! And, that's with a CPU running at 14MHz!!!! That's the difference a good OS makes, and OS4 is built to give the same advantages with modern additions.
Fair enough the PC hardware (mobo/CPU) is cheaper to buy, but the Amiga has proved that you don't need to have the latest/fastest h/w to do usefull work with a computer...
What can I say; if I had £1000 to spend on new computer kit, I'd get the A1 G4/800, 512MB RAM, 40GB HD, slap in my spare Matrox G400, 17"CTX monitor, case, sound card - with a good £180 still to go!
And if you don't think that's worth it, and worth buying, then do you belive the Amiga has any future other than as a retro-gaming has-been? Because I do!
Brothers and sisters, I have a dream! It's name is Amiga.