HQ4X and Ours are the clear winners if you must resample like this; the downsides are that HQ4X occasionally has jaggies and Ours makes makes a lot of fine details look "blobby".
Regarding HQ4X, they used the algorithm to create 4X image but used Nearest neighbor to create 8X and 16X images. I think doing HQ4X two times would have resulted into a better 16X images without jags.
The Vector Magic results reminded me a lot of this: http://www.cowboybooks.com.au/html/acidtrip1.html