Yes, it is worthwhile.
There are now many free sample sets. Many famous organs have been recorded in the last years and the producer often releases a demo containing a few beautiful stops. Some people (including me, some time ago) have been working on composite sample sets that combine multiple demo's to get a very complete disposition, which works very well. These composite sample sets are also freely available.
Updating to a newer computer and HW4.2 Advanced comes therefore with a present: you will be able to enjoy many excellent sample sets for free. I recommend a minimum of 8 GB RAM, preferably 16 GB (or at least 32GB if you want to invest in recent top-quality commercial sample sets). Only the advanced edition of HW will take advantage of these large amounts of RAM.