Wondering if there is any major pros going with the 512mb version?  Trying to keep a budget build and the extra $30-40 makes a difference.  But is the price/performance for the 512mb that much better?  
 
I noticed the charts on toms has only the 256 version.  Thanks.

256 version is going to get murdered if you play in resolutions higher than 1280x1024. So, if you play 1440x900 or greater, then you definitely want the 512MB version.

512 is much better in many tests
 
as noted by rgeist

There has been a tendancy recently for newer releases requiring 512 (well it says that on the back of the box).
As rgeist554 says "256 version is going to get murdered if you play in resolutions higher than 1280x1024".
The way i would have put it is that you will get away with a 256 card up to a resolution of 1280x1024.
If you like you can post the other specs and we can see if we can shave enough of elsewhere with out hitting performance too much so you can get the 512 card, Which will hold you for a bit longer in terms of future playable games.
  Mactronix  
 Ps what size screen and what resolution are the main key here.

Thanks for responding.
 
Well, originally I was going to get a 19" widescreen due to the price.  Coming from a notebook, 19" seemed large to me at first but now I realize the widescreen cuts down on that size a little bit and has low rez.  So I found a CHIMEI CMV 221D 22" wide screen for $239 (209 AR).  Now I see the resolution is 1680 x 1050 and from your posts above a 256mb might be underpowered.  

Yeah, 256MB will definitely be underpowered for that resolution.

 Definatly : So the thing is now can you streatch to the 512 without compramise else where ?
     Mactronix

Well the cheapest 3850 512mb on newegg is 199 (179 AR).  So I might drop down to a AMD 4200+, 160GB instead of 250GB, and/or 430W instead of 500W PSU.
 
Or I could get a 20" widescreen instead of 22".  lol.  Its tough to come up with a comprise.  I really need to stop thinking $$$ now, but instead realize that in a few years when Im ready to upgrade again, I can keep my case, PSU, monitor, and perhaps a MOBO if its quad core ready....

Native resolution of a 20" is still 1680x1050. Not gonna help you on cutting back the graphics demand.

Tru.  I'm now set on getting a 3850 512 for sure.  But the 20" might save me 30 bucks.
 
Just discovered clubit.com.  A 20" CHIMEI is $160. Cheap price. The 22" 194.

 Are you set on wide screen because 19 inch at 4:3 =native res of 1280x1024.
Dont skimp on the psu either if thats weak the whole system is weak.
Drop the Hard Drive down to 120 obviously is another easy saver.
Without knowing more about what you are planning on using its a bit hard to suggest any thing else.
   Mactronix

Dont get a 256mb card of any sort.  512mb is the future, take a look at the system requirements for Assassin's Creed, thats the direction we're headed in.  
 
On a side note, I remember being shocked when I saw that Battlefield 2 wanted a minimum of 128mb graphics memory.  Oh how times change.

Mact,
 
Trying for a budget gaming build and an update to my 5 year old notebook.  Casual gaming, poker, internet, music.  
 
CPU:  4400+ AMD Dual Core.  Don't know if I should step down to 4000+.
Video:  DEFINITELY a 3850 512MB.  Will get the cheapest one available on egg probably.
HD:  160 GB
Case: Anything really with 2 fans.  Missed out on a coolermaster for $9 yesterday. Bummed about that deal.
RAM: 2 GB.  Thinking about going to 4GB
OS:  Vista 64.  I don't to buy XP only to upgrade it later to Vista.
PSU:  Looking at Antec Earthwatts, either 430W or 500W.  Some people say you can power an 8800 with just 380W.      
         from what I understand the 3850 uses less power.  So I might be OK with the 430W.
CD/DVD:  Any decent retail version ~$32
Monitor:  Might as well get a 22" for future and since the 3850 will power it nicely.
MOBO:  Only thing I really am unsure about.  I was thinking about getting a Biostar TA770 A2+ for $80.  It is compatible with phenom so a future upgrade would be easy with that mobo.  Or I can just get a 690G mobo for a little bit less.
 
Priced a system like above for around ~820.  I don't think I could do much cheaper.  The only big X factor is the GPU, but thats something I need to splurge on.

 I would keep it as close to what you have if i was you the MOBO i would definitely get the upgradable one you will thank yourself later. I guess if you had to you could drop the CPU down with a view to upgrading it later but only do it if you have to. Ram well i personally would want 4 to run vista  but i am still running XP and will be putting it on my next build in a couple of months as well, Just personal preference though 2 gig is enough to run vista.
Good news on the PSU you can indeed get the 430 its got 3 12v rails totaling 32Amps which is plenty.
 Think that's about it again only on a personal preference note i would have gone for a 4:3 19 inch but that's just me.
    Enjoy your build hope all goes well.
          Mactronix