Any particular problem with Altus? Seems well matched to the bike and unless damaged there is little upside to a change.
Now if you intended to tighten up the steps on the 7 spd by going to 9 or 10 spd that is another but considerably more
expensive choice but Sora and Tiagra are still out as triples (Tiagra as NOS with the recent 11spd removing the triple).
There are ATB shifters for T bars that will work fine with road groups upto 9 spd.