I actually "disagree" slightly, which is not very important as we're talking opinions here, but still. I bought the Numidian Infantry box from Wargames Factory, mainly for the bows (...) and while it is a good kit for a low price it is still vastly inferior to the detail a GW miniature of the newest generation possesses. I love Kislev and thought about The Assault Group, but I feel the same about their miniatures. Their horses especially are very low on detail/coolness in my opinion. If you want 'modest' miniatures that don't scream fantasy the alternative companies may be your thing (for historical they are obviously better), but I really don't see them approaching the detail and character of Games Workshop. Nor do I think they fit the Warhammer world as I envisage it (GW suckered me for real!). You pay through the nose, but you get quality is how I see it.
For Kislev mini's I would therefore recommend (but again: taste!!) combinations of GW kits. I am in the process of building Horse Archers using Marauder Horsemen + Archers + WF bows; I am thinking of building Lancers using pistolier horses + legs + torso's, but I don't know yet which arms, lances and heads I should choose. The wings are another challenge. This may sound expensive, but if you use left-over parts for other projects it really isn't that bad. For example, the the Marauder parts I won't use (arms, weapons) could enhance my knights or be the start of a Kossar conversion. Also the cost for the old school Kislevites is mostly downright prohibitive.
These are just my ideas though, looking forward to different ones!