I own the 50 watt version, but listened to the 70 watt version. The 70 watt version sounds very similar to the (stock) 50 watter except it is a little smoother through the mids. The 70 watter adds better 6922 tubes. Not much difference in power...20 watt difference is not enough to hear. However, if you add a good pair of 6922 input tubes to the stock 50 watter...wow, look out! I replaced the stock tubes (Golden Dragon ECC86 - decent, but nothing special) with NOS Amperex PQ orange label 6922 with gold pins. The difference is quite dramatic. So, if you can pick up a 50 watter, just add some good 6922's to it and save the extra money you would have spent on the 70 watter. BTW, high performance 6922's should run any where from $50 to $150 for the pair depending on rarity, age, hours, etc.