I have noticed that a dual-core (or higher) CPU will perform much better in this respect, as only 50% of capacity will be taken up by one process.
I notice this particularly with AV scans and updates (similarly disk / CPU intensive to indexing).
While performing an identical task (updating Sophos), one PC (single core) is slowed to a virtual standstill with 99-100% CPU, the other (dual-core) is still usable with approx. 50% utilisation.
SD