Injection is listed at 3.3 oz. Small Sebenza 21 is listed at 3 oz. So should not be a huge deal... As it would have it I was actually browsing Knives for myself, and when I came across the Injection again I immediately thought back to this thread. Because of your high budget we all naturally gravitate towards fancier and more expensive options at the upper end of your budget, but i noticed the blade profile and belly is something like a cross between the delica and sebbie21, the flat ground blade is also very thin, also in between the two, as well as the handle length, but it is just a bit more robust thhn the sebbie's, with a 3" blade it pretty much hits every mark you were looking for.
As for what to expect from the steel, I mean, when properly made and heat treated, its a decent average grade knife steel. Think a good 440(a) or aus8, sandvik 14c28n like in the standard usa Kershaw's, all decent but basic stainlesses in the same "range" regarding performance. Nothing "wow" factor about them, but nothing disappointing either, they do the job well. Problem with it (being the Chinese equivelant of that grade of steel) is quality control measures, some companies are (much) worse then others, but I gotta say, so far I have quite a few bargain blades made from 8cr13mov; a few crkt's, a Kilimanjaro, a few schrade's, as well as a few kershaw's; Thermite, Tremor, recently gave away a pair of Shuffles, recently acquired a Scrambler, and hands down the Kershaw's are without a doubt the best if the bunch. They get razor sharp, and they hold an edge respectably well, especially when considering price. Thats why I said it might surprise you... Not to mention alongside your sebbie and delica, and leek and chaparral should you keep them, having a cheap "insurance" option in your collection as an alternative edc at your disposal isn't a bad thing...
The opinel idea isn't a bad one either, being a French manufacturer you may be able to get good deals on them locally around Europe? I never owned one, but many who do swear by them, they're convex ground, lightweight, and I do know sandvik 12c27 they use a really decent basic all around knife steel as well.