2000+Thorton or locked 2500+Barton?

Im building a system for my bro so i dont wana spend on it a lot of money like i did with my own rig.

Its gona consist of:
NF7-S v2.0
Ati Radeon 9600XT
2x256 XMS PC 3200
Fortron 350W PSU
Raptor 36GB (or maybe 2 if price permits)
etc... (not interesting stuff)

Now im in a dilemma:
Shall i take a 2500+ Barton or a 2000+Thorton
Price difference is only about $30 so thats not the case,
i only need the best OCer.
The questions i have and i would be very very thankfull if u could answer are:

1.IS Thortons multy locked?
2.IS there any mod to unlock the rest of the cache in Thorton?
3.What is the best oc for locked barton on air ?
(i may afford a SP-97 and duct a tornado to it like i did with my 64bit system)
4.In any case, can i leave my memory 1:1?

Thanks in advance to everybody that's kind enough to respond!

I have both CPUs, so here's what I have to say:

1. All CPUs made after weeks 40-41 are locked; that includes Bartons, Thortons, Tbreds, Durons etc.

2. You can unlock the extra cache only if your CPU isn't multiplier locked. My Thorton XP 2000+ is week 41, and is both multiplier and cache locked. But even if it weren't locked, you should think if you really want to unlock the extra cache, as it'll bring down the max speed your CPU can reach.

3. My XP2500+ is unlocked, and reaches 2300MHz on air (Zalman cooler, 200x11.5) with keeping the temp under 50 degrees; for some reason, the Thorton is pumping out a bit more heat than the 2500, so I can't get the voltage too high with this setup; I can keep it stable and under 50 degrees at 1.75V, 174 FSB, which means 2175 MHz on the CPU. I'm sure it could go higher though with better cooling (I'm thinking of modding my Zalman). If the Barton were locked, depending on the memory, it could still reach 2300 at 210X11. So overall, the 2500+ gives me better results in this setup, because it goes higher and has larger cache.

Again, with better cooling the results could be different.

What will be the limiting factor on your FSB only overclock is going to be motherboard and RAM related. most bartons max out anywhere between 2.4 and 2.5GHz, some do more others do less. so you should get RAM that will allow 218-227MHz FSB at decent timings.
About unlocking the thorton's cache, as already mentioned above. If your CPU is week 38 and earlier you have a great chance of tunring it back to a barton, if its week 39-40 the chances are slim, 41 and up are almost all locked.
If the chip is locked there's no modding or whatever that you can do to enable the extra cache.
One thing to note tho, the Barton 2500+ has an x11 multi, the Thorton has x12. the newest stepping will both max at about the same speed, so considering the money you want to invest into RAM you can get cheaper RAM for the Thorton, get it to the same speed, but you will lose FSB MHz

Actually the 2000+ Thortons are locked at 12.5x, not 12x

first, thank you very much for the replies,

So basically that means thorton is gona oc better for the 12.5x multy vs 11x for barton.
Since ill get good cooling and good ocable ram, plus the fact that nf7-s can dig around 220-225,
2242-2475 for the barton,
2750-2812 for the thorton...
Now can the thorton possibly take 2750+mhz???
Remember its gona be air cooled with sp-97 heatpipe and ducted tornado.
And if so, will it perform better in games than the 2450 Barton?

EDIT: too bad that i wont find any unlocked chips in retail...

I'd have to say 2.7 on air seems far fetched. 2.4-2.5 maybe, but unless you go to some type of more extreme cooling, I don't think you'll get higher than that.

And no, you probably won't be able to tell the difference in games between 2.5 and 2.7