There are not that many tubes in a line stage. Preamp tubes last a long time and are not that expensive as long as you buy current production. There are no expensive power tubes to replace. So the tube replacement costs of an ARC should not be that much more expensive than the Peachtree. Tube amps are where it can get expensive to re tube.
That said, I would not purchase any preamp without hearing it in my system. An excellent preamp can sound bad if matched with the wrong amp. System synergy is very important. If you are planning on upgrading your amp in the not too distant future. The I would decide on a upgrade plan for both.