I tried to restrain myself from making negative comments about the Grado SR60, however I have had it for many years and hated it. I finally gave it away. I didn’t even try to sell it. The highs on it were harsh and painful. It leaked plenty of sound, and had a huge and heavy cord. Perhaps my SR60 might have been defective? I still have the SR80, which has much better highs and better bass, but imo still isn’t a great headphone. Imo the cheaper Sony V6 sounds much better.
I have had the Koss Portapro for over 10 years. imo the Portapro sounds much worse than the Sennheiser PX100. Imo even the JVC HAS160 which is under $15 sounds much better than the Portapro. If someone really loves the Portapro sound though, they can get almost exactly the same sound for half the price by buying the Sportapro. The HAS160 has better highs than the Portapro or PX100, however the PX100 has better bass. The Portapro and Sportapro sounds muddy at times, which isn’t an issue on the PX100 or HAS160(could the PX100 mk2 sound muddy at times?). i used to like the Portapro and Sportapro many years ago, until I found better lower cost alternatives.
It is funny that you mention the Koss KTX pro1. I actually like the sound quality on the KTXpro1 much better than the Portapro, as it has much better highs, and the bass doesn’t sound muddly. The latest version of the KTXpro1 looks very cheap though. Why don’t they make it all black like they did in the past?
As for Sony, the under $10 Sony MDR-E828 earbuds sound great for the price. They have good bass and good highs, although the midrange isn’t that great(hey, they can’t give you everything for under $10). The Sony V6 is one of the best headphones under $100, however very recently its price on Amazon went up from $65 to $80(will it drop back to $65 or less in January?). Some of the more expensive Sony headphones are also nice. Some of the lower priced Sony headphones are awful though.
I don’t know which Sennheiser headphones disappointed you. The only Sennheiser headphones or earbuds that disappointed me were the MX300 earbuds. I have had well over a dozen Sennheiser models over the years. The Sennheiser MX580 earbuds at under $25 are a great value. Imo they are close in quality to the Sony E-888 earbuds which are at least $75 if you can find them.