I own several DAPs, they just can't beat the convivence of dongles. So I bought several, from $100 ones to $400 ones. W4 is probably the only dongle you need. I also have the W2, bought from MusicTeck as well. W4 is an improvement from every aspect of W2: better details, lower power consumption, higher output power, more expanded stage. The W2 is still a very good device. But the fact that it is discontinued right now and there is W4 existing makes W2 an obvious inferior choice to W4. If you have the budget for W4, or simply want to try the best that a dongle could offer, you will not be disappointed by this device. Also, this dongle is beautifully made, the original leather case is very pretty too.
Like always, MusicTeck is a great website to buy from. Shipment is always so fast and more importantly, the packaging is really nice: always wrapped in bubbles and tightly sealed.