This is not possible in standard that you can track budget on ARC/PO based/Contract based.
You can track budget on the basis of fund center/ commitment item(G/L) and FUND center can be cost center/ profit center/AUCs etc.
So for your requirement you can do one think that you create cost center for every ARCs and create it as fund center and assign budget then track. When you create ARC please make with account assignment 'K' and enter respective cost center.
But this is not recommended because you have to create cost center for every ARCs.