If you liked the U4, definitely should try out the shrimps. Feels very close to the u4 68g in terms of firmness but smoother on the up/down stroke. The bump is slightly more distinct. Just wish they would offer it with lighter springs.
On the cheaper and lighter bump end, I'd recommend either Wuque/Haimu silent tactiles. Very smooth and silent but you're giving about 50% of the bump, but great for office environments and fast typing.