Hi
Although AlienWare make good PCs( relativley) you are better of building your own. If you dont feel comfortable with that consider getting ready-built PC.
In terms of standards:
There wont be any 'revolution' in PC standards - there probaably will be a slow upgrade to 64biy systems however.
If you are building a PC in the next few months my advice would be to forget 64bit CPUs; they are in their infancy in terms of performance and support.
Get you self an AMD Barton processor(cheaper but run hotter than Intel so will need more cooling). These processors range from 2500+ (which can be overclocked to 3200+) to 3400+ ( which can be overlclocked to something even higher). The 2500+ will set you back about 50-60 quid while a top-of-the-range Barton will set you back ~ £150 ( I think). Depending on you budget I would probably go for a 2500+; that is more than enough for even the most demanding games ( coupled with a good GFX card

)
Motherboard wise I think it is safe to buy a know as I dont see any major revolution coming up anytime soon. The best mobo around (for the price) is the Abit NF7-s. It supports any kind of Barton CPU, has Serial ATA Raid, Soundstorm onboard audio ( v. good for a PC --->5.1 speakers ~ SB Audigy), supports up to 3GB DDR 400 RAM, 10/100 LAN, has AGP x8 and is a good overclocker (i.e goodbios and ocing options). This will set you back £60
RAM. RAM is dirt cheap at the mo. 1GB of Dual Channel DDR 400 RAM ( that has low latency i,e overclocks well) will set you back arounf £160. This should set you up for at least 2 years.
GFX. This is a very important component. It is also the most difficult to address at the moment. The new generation of GFX card are coming out in April/May. Nvidia and ATI are bringing out chips which will be ultra fast (supposedly). These chips coupled with a decent processor should be able to push the frame rate of games such as Half Life 2 and Doom III into the hundreds ( in my opinion - that is if they live up to all the hype). It is a very hard decision wether to upgrade now or not. I dicided to upgrade now ( i had a GF4ti4200, now I have a powercolor ATI radeon 9800 non pro ( which I will be flashing to a pro

) I bought this card for 140 a week ago. Already the pro version of my card which costed 160 quid now cost 140 ( at Komplett). I am hoping that this card will last me at leats a 1-2 years.
The reasoning behind me buying my GFX card now is that when the new gen card come out they will be really expensive (300-400quid) for a few months. Only after a few months have passed will ATI NVIDIa reduce their prices. In short if you want to buy a GFX card now you wont go far wrong- get a ATI Radeon 9800 Pro. If you think you will have lots of money in a few months time and you wont be playing games now then wait and get a next gen card when they come out. The choice is yours but to more research before you make it.
Hardrive wise no real innovations their. The different standards HD (i.e ATA 33 66 100 133) are all a bit of a joke. My ATA 100 drive can output around 50mb/s on average. My advice is to get two Serial ATA (SATA) and wire them up in RAID 0. This way you will get more speed out of them. HD are usually bottlenecks in fast systems.
All other stuff you might want to get depend on what you want you pc for... If you want me to spec you one then post here. Hope my ramblings are helpfull.
p.s all in all you are looking at arounf 600 hundred for a PC that will be just as good as a AW( that is without the screen)