From me as a buyer’s view:
I follow all authors, who have – for my taste – more than one good (and I mean: very good) theme.
I prefer professional business WP themes and portfolios for artists, but mostly I work with Wordpress.
PSD themes are nearly worthless for me, HTML themes causes too much time and work for me, because my contents are too huge for just HTML sites.
But I love good Wordpress themes with professional design and not too much “bling bling”
If you have more than one, I be your follower
It just depends on your own work and cannot be “forced”